How to get the IP address of the server on which my C application is running on

Question

I am running a server  and I want to display my own IP address   What is the syntax for getting the computer s own  if possible  external  IP address   Someone wrote the following code   IPHostEntry host  string localIP        host   Dns GetHostEntry Dns GetHostName     foreach  IPAddress ip in host AddressList        if  ip AddressFamily ToString       InterNetwork                 localIP   ip ToString            return localIP    However  I generally distrust the author  and I don t understand this code  Is there a better way to do so

User · Answer

The only way to know your public IP is to ask someone else to tell you  this code may help you   public string GetPublicIP         String direction           WebRequest request   WebRequest Create  http   checkip dyndns org         using  WebResponse response   request GetResponse        using  StreamReader stream   new StreamReader response GetResponseStream                   direction   stream ReadToEnd                 Search for the ip in the html     int first   direction IndexOf  Address       9      int last   direction LastIndexOf   lt  body gt         direction   direction Substring first  last - first        return direction

User · Answer

If you can t rely on getting your IP address from a DNS server  which has happened to me   you can use the following approach   The System Net NetworkInformation namespace contains a NetworkInterface class  which has a static GetAllNetworkInterfaces method   This method will return all  network interfaces  on your machine  and there are generally quite a few  even if you only have a wireless adapter and or an ethernet adapter hardware installed on your machine   All of these network interfaces have valid IP addresses for your local machine  although you probably only want one   If you re looking for one IP address  then you ll need to filter the list down until you can identify the right address   You will probably need to do some experimentation  but I had success with the following approach    Filter out any NetworkInterfaces that are inactive by checking for OperationalStatus    OperationalStatus Up   This will exclude your physical ethernet adapter  for instance  if you don t have a network cable plugged in    For each NetworkInterface  you can get an IPInterfaceProperties object using the GetIPProperties method  and from an IPInterfaceProperties object you can access the UnicastAddresses property for a list of UnicastIPAddressInformation objects    Filter out non-preferred unicast addresses by checking for DuplicateAddressDetectionState    DuplicateAddressDetectionState Preferred Filter out  virtual  addresses by checking for AddressPreferredLifetime    UInt32 MaxValue    At this point I take the address of the first  if any  unicast address that matches all of these filters   EDIT    revised code on May 16  2018 to include the conditions mentioned in the text above for duplicate address detection state and preferred lifetime   The sample below demonstrates filtering based on operational status  address family  excluding the loopback address  127 0 0 1   duplicate address detection state  and preferred lifetime   static IEnumerable lt IPAddress gt  GetLocalIpAddresses            Get the list of network interfaces for the local computer      var adapters   NetworkInterface GetAllNetworkInterfaces            Return the list of local IPv4 addresses excluding the local        host  disconnected  and virtual addresses      return  from adapter in adapters             let properties   adapter GetIPProperties               from address in properties UnicastAddresses             where adapter OperationalStatus    OperationalStatus Up  amp  amp                    address Address AddressFamily    AddressFamily InterNetwork  amp  amp                     address Equals IPAddress Loopback   amp  amp                    address DuplicateAddressDetectionState    DuplicateAddressDetectionState Preferred  amp  amp                    address AddressPreferredLifetime    UInt32 MaxValue             select address Address

User · Answer

namespace NKUtilities        using System      using System Net      using System Net Sockets       public class DNSUtility               public static int Main string    args                        string strHostName                   try                    if args Length    0                                           Getting Ip address of local machine                           First get the host name of local machine                      strHostName   Dns GetHostName                        Console WriteLine   Local Machine s Host Name       strHostName                                     else                                          Otherwise  get the IP address of the host provided on the command line                      strHostName   args 0                                         Then using host name  get the IP address list                   IPHostEntry ipEntry   Dns GetHostEntry  strHostName                   IPAddress    addr   ipEntry AddressList                   for int i   0  i  lt  addr Length  i                                          Console WriteLine  IP Address  0    1     i  addr i  ToString                                       return 0                              catch SocketException se                                 Console WriteLine   0    1     se Message  strHostName                   return -1                             catch Exception ex                                 Console WriteLine  Error   0     ex Message                   return -1                                    Look here for details   You have to remember your computer can have more than one IP  actually it always does  - so which one are you after

User · Answer

To get the remote ip address the quickest way possible  You must have to use a downloader  or create a server on your computer   The downsides to using this simple code   which is recommended  is that it will take 3-5 seconds to get your Remote IP Address because the WebClient when initialized always takes 3-5 seconds to check for your proxy settings    public static string GetIP                  string externalIP                   externalIP   new WebClient   DownloadString  http   checkip dyndns org                 externalIP    new Regex    d 1 3    d 1 3    d 1 3    d 1 3                                                 Matches externalIP  0  ToString                return externalIP       Here is how I fixed it    first time still takes 3-5 seconds  but after that it will always get your Remote IP Address in 0-2 seconds depending on your connection   public static WebClient webclient   new WebClient    public static string GetIP         string externalIP           externalIP   webclient DownloadString  http   checkip dyndns org         externalIP    new Regex    d 1 3    d 1 3    d 1 3    d 1 3                                         Matches externalIP  0  ToString        return externalIP

User · Answer

using System  using System Net   namespace IPADDRESS       class Program               static void Main string   args                        String strHostName   string Empty              if  args Length    0                                                   First get the host name of local machine                    strHostName   Dns GetHostName                    Console WriteLine  Local Machine s Host Name      strHostName                             else                               strHostName   args 0                                Then using host name  get the IP address list                 IPHostEntry ipEntry   Dns GetHostByName strHostName               IPAddress   addr   ipEntry AddressList              for  int i   0  i  lt  addr Length  i                                  Console WriteLine  IP Address  0    1     i  addr i  ToString                               Console ReadLine

User · Answer

It works for me    and should be faster in most case  if not all  than querying a DNS server  Thanks to Dr  Wily s Apprentice  here                                                                                     lt summary gt      Will search for the an active NetworkInterafce that has a Gateway  otherwise     it will fallback to try from the DNS which is not safe       lt  summary gt       lt returns gt  lt  returns gt  public static NetworkInterface GetMainNetworkInterface         List lt NetworkInterface gt  candidates   new List lt NetworkInterface gt          if  NetworkInterface GetIsNetworkAvailable                  NetworkInterface   NetworkInterfaces               NetworkInterface GetAllNetworkInterfaces             foreach               NetworkInterface ni in NetworkInterfaces                        if  ni OperationalStatus    OperationalStatus Up                  candidates Add ni                        if  candidates Count    1                return candidates 0                 Accoring to our tech  the main NetworkInterface should have a Gateway         and it should be the ony one with a gateway      if  candidates Count  gt  1                for  int n   candidates Count - 1  n  gt   0  n--                        if  candidates n  GetIPProperties   GatewayAddresses Count    0                                candidates RemoveAt n                                    if  candidates Count    1                        return candidates 0                           Fallback to try by getting my ipAdress from the dns     IPAddress myMainIpAdress   null      IPHostEntry host   Dns GetHostEntry Dns GetHostName         foreach  IPAddress ip in host AddressList                if  ip AddressFamily    AddressFamily InterNetwork     Get the first IpV4                       myMainIpAdress   ip              break                       if  myMainIpAdress    null                NetworkInterface   NetworkInterfaces               NetworkInterface GetAllNetworkInterfaces             foreach  NetworkInterface ni in NetworkInterfaces                        if  ni OperationalStatus    OperationalStatus Up                                IPInterfaceProperties props   ni GetIPProperties                    foreach  UnicastIPAddressInformation ai in props UnicastAddresses                                        if  ai Address Equals myMainIpAdress                                                 return ni                                                                             return null                                                                                lt summary gt      AddressFamily InterNetwork   IPv4     Thanks to Dr  Wilys Apprentice at     http   stackoverflow com questions 1069103 how-to-get-the-ip-address-of-the-server-on-which-my-c-sharp-application-is-runni     using System Net NetworkInformation       lt  summary gt       lt param name  mac  gt  lt  param gt       lt param name  addressFamily  gt AddressFamily InterNetwork   IPv4   AddressFamily InterNetworkV6   IPv6 lt  param gt       lt returns gt  lt  returns gt  public static IPAddress GetIpFromMac PhysicalAddress mac  AddressFamily addressFamily   AddressFamily InterNetwork        NetworkInterface   NetworkInterfaces           NetworkInterface GetAllNetworkInterfaces         foreach  NetworkInterface ni in NetworkInterfaces                if  ni GetPhysicalAddress   Equals mac                         if  ni OperationalStatus    OperationalStatus Up                                IPInterfaceProperties props   ni GetIPProperties                    foreach  UnicastIPAddressInformation ai in props UnicastAddresses                                        if  ai DuplicateAddressDetectionState    DuplicateAddressDetectionState Preferred                                                if  ai Address AddressFamily    addressFamily                                                        return ai Address                                                                                                       return null                                                                                lt summary gt      Return the best guess of main ipAdress  To get it in the form aaa bbb ccc ddd just call         ToString          on the result       lt  summary gt       lt returns gt  lt  returns gt  public static IPAddress GetMyInternetIpAddress         NetworkInterface ni   GetMainNetworkInterface        IPAddress ipAddress   GetIpFromMac ni GetPhysicalAddress         if  ipAddress    null     could it be possible                 ipAddress   GetIpFromMac ni GetPhysicalAddress    AddressFamily InterNetworkV6              return ipAddress                                                                             Just as reference this is the full class code where I defined it   using System  using System Collections Concurrent  using System Collections Generic  using System Diagnostics  using System Linq  using System Net  using System Net NetworkInformation  using System Net Sockets  using System Runtime InteropServices  using System Threading Tasks   namespace TcpMonitor                  Usage                  var cons   TcpHelper GetAllTCPConnections                    foreach  TcpHelper MIB TCPROW OWNER PID c in cons                  public class NetHelper                DllImport  iphlpapi dll   SetLastError   true           static extern uint GetExtendedUdpTable IntPtr pUdpTable  ref int dwOutBufLen  bool sort  int ipVersion  UDP TABLE CLASS tblClass  uint reserved   0            public enum UDP TABLE CLASS                       UDP TABLE BASIC              UDP TABLE OWNER PID              UDP TABLE OWNER MODULE                     StructLayout LayoutKind Sequential           public struct MIB UDPTABLE OWNER PID                       public uint dwNumEntries               MarshalAs UnmanagedType ByValArray  ArraySubType   UnmanagedType Struct  SizeConst   1               public MIB UDPROW OWNER PID   table                      StructLayout LayoutKind Sequential           public struct MIB UDPROW OWNER PID                       public uint localAddr               MarshalAs UnmanagedType ByValArray  SizeConst   4               public byte   localPort              public uint owningPid               public uint ProcessId                               get   return owningPid                               public IPAddress LocalAddress                               get   return new IPAddress localAddr                                public ushort LocalPort                               get   return BitConverter ToUInt16 localPort Take 2  Reverse   ToArray    0                                       StructLayout LayoutKind Sequential           public struct MIB UDP6TABLE OWNER PID                       public uint dwNumEntries               MarshalAs UnmanagedType ByValArray  ArraySubType   UnmanagedType Struct  SizeConst   1               public MIB UDP6ROW OWNER PID   table                      StructLayout LayoutKind Sequential           public struct MIB UDP6ROW OWNER PID                        MarshalAs UnmanagedType ByValArray  SizeConst   16               public byte   localAddr              public uint localScopeId               MarshalAs UnmanagedType ByValArray  SizeConst   4               public byte   localPort              public uint owningPid              public uint ProcessId                               get   return owningPid                               public IPAddress LocalAddress                               get   return new IPAddress localAddr  localScopeId                                public ushort LocalPort                               get   return BitConverter ToUInt16 localPort Take 2  Reverse   ToArray    0                                      public static List lt MIB UDPROW OWNER PID gt  GetAllUDPConnections                         return GetUDPConnections lt MIB UDPROW OWNER PID  MIB UDPTABLE OWNER PID gt   AF INET                      public static List lt MIB UDP6ROW OWNER PID gt  GetAllUDPv6Connections                         return GetUDPConnections lt MIB UDP6ROW OWNER PID  MIB UDP6TABLE OWNER PID gt  AF INET6                      private static List lt IPR gt  GetUDPConnections lt IPR  IPT gt  int ipVersion   IPR   Row Type  IPT   Table Type                       List lt IPR gt  result   null               IPR   tableRows   null              int buffSize   0               var dwNumEntriesField   typeof IPT  GetField  dwNumEntries                    how much memory do we need              uint ret   GetExtendedUdpTable IntPtr Zero  ref buffSize  true  ipVersion  UDP TABLE CLASS UDP TABLE OWNER PID               IntPtr udpTablePtr   Marshal AllocHGlobal buffSize                try                               ret   GetExtendedUdpTable udpTablePtr  ref buffSize  true  ipVersion  UDP TABLE CLASS UDP TABLE OWNER PID                   if  ret    0                      return new List lt IPR gt                         get the number of entries in the table                 IPT table    IPT Marshal PtrToStructure udpTablePtr  typeof IPT                    int rowStructSize   Marshal SizeOf typeof IPR                    uint numEntries    uint dwNumEntriesField GetValue table                       buffer we will be returning                 tableRows   new IPR numEntries                    IntPtr rowPtr    IntPtr   long udpTablePtr   4                   for  int i   0  i  lt  numEntries  i                                          IPR tcpRow    IPR Marshal PtrToStructure rowPtr  typeof IPR                        tableRows i    tcpRow                      rowPtr    IntPtr   long rowPtr   rowStructSize        next entry                                             finally                               result   tableRows  ToList      new List lt IPR gt                         Free the Memory                 Marshal FreeHGlobal udpTablePtr                              return result                      DllImport  iphlpapi dll   SetLastError   true           static extern uint GetExtendedTcpTable IntPtr pTcpTable  ref int dwOutBufLen  bool sort  int ipVersion  TCP TABLE CLASS tblClass  uint reserved   0              public enum MIB TCP STATE                       MIB TCP STATE CLOSED   1              MIB TCP STATE LISTEN   2              MIB TCP STATE SYN SENT   3              MIB TCP STATE SYN RCVD   4              MIB TCP STATE ESTAB   5              MIB TCP STATE FIN WAIT1   6              MIB TCP STATE FIN WAIT2   7              MIB TCP STATE CLOSE WAIT   8              MIB TCP STATE CLOSING   9              MIB TCP STATE LAST ACK   10              MIB TCP STATE TIME WAIT   11              MIB TCP STATE DELETE TCB   12                    public enum TCP TABLE CLASS                       TCP TABLE BASIC LISTENER              TCP TABLE BASIC CONNECTIONS              TCP TABLE BASIC ALL              TCP TABLE OWNER PID LISTENER              TCP TABLE OWNER PID CONNECTIONS              TCP TABLE OWNER PID ALL              TCP TABLE OWNER MODULE LISTENER              TCP TABLE OWNER MODULE CONNECTIONS              TCP TABLE OWNER MODULE ALL                     StructLayout LayoutKind Sequential           public struct MIB TCPTABLE OWNER PID                       public uint dwNumEntries               MarshalAs UnmanagedType ByValArray  ArraySubType   UnmanagedType Struct  SizeConst   1               public MIB TCPROW OWNER PID   table                      StructLayout LayoutKind Sequential           public struct MIB TCP6TABLE OWNER PID                       public uint dwNumEntries               MarshalAs UnmanagedType ByValArray  ArraySubType   UnmanagedType Struct  SizeConst   1               public MIB TCP6ROW OWNER PID   table                      StructLayout LayoutKind Sequential           public struct MIB TCPROW OWNER PID                       public uint state              public uint localAddr               MarshalAs UnmanagedType ByValArray  SizeConst   4               public byte   localPort              public uint remoteAddr               MarshalAs UnmanagedType ByValArray  SizeConst   4               public byte   remotePort              public uint owningPid               public uint ProcessId                               get   return owningPid                               public IPAddress LocalAddress                               get   return new IPAddress localAddr                                public ushort LocalPort                               get                                       return BitConverter ToUInt16 new byte 2    localPort 1   localPort 0     0                                                public IPAddress RemoteAddress                               get   return new IPAddress remoteAddr                                public ushort RemotePort                               get                                       return BitConverter ToUInt16 new byte 2    remotePort 1   remotePort 0     0                                                public MIB TCP STATE State                               get   return  MIB TCP STATE state                                       StructLayout LayoutKind Sequential           public struct MIB TCP6ROW OWNER PID                        MarshalAs UnmanagedType ByValArray  SizeConst   16               public byte   localAddr              public uint localScopeId               MarshalAs UnmanagedType ByValArray  SizeConst   4               public byte   localPort               MarshalAs UnmanagedType ByValArray  SizeConst   16               public byte   remoteAddr              public uint remoteScopeId               MarshalAs UnmanagedType ByValArray  SizeConst   4               public byte   remotePort              public uint state              public uint owningPid               public uint ProcessId                               get   return owningPid                               public long LocalScopeId                               get   return localScopeId                               public IPAddress LocalAddress                               get   return new IPAddress localAddr  LocalScopeId                                public ushort LocalPort                               get   return BitConverter ToUInt16 localPort Take 2  Reverse   ToArray    0                                public long RemoteScopeId                               get   return remoteScopeId                               public IPAddress RemoteAddress                               get   return new IPAddress remoteAddr  RemoteScopeId                                public ushort RemotePort                               get   return BitConverter ToUInt16 remotePort Take 2  Reverse   ToArray    0                                public MIB TCP STATE State                               get   return  MIB TCP STATE state                                      public const int AF INET   2        IP v4   System Net Sockets AddressFamily InterNetwork         public const int AF INET6   23      IP v6   System Net Sockets AddressFamily InterNetworkV6          public static Task lt List lt MIB TCPROW OWNER PID gt  gt  GetAllTCPConnectionsAsync                         return Task Run      gt  GetTCPConnections lt MIB TCPROW OWNER PID  MIB TCPTABLE OWNER PID gt  AF INET                       public static List lt MIB TCPROW OWNER PID gt  GetAllTCPConnections                         return GetTCPConnections lt MIB TCPROW OWNER PID  MIB TCPTABLE OWNER PID gt  AF INET                      public static Task lt List lt MIB TCP6ROW OWNER PID gt  gt  GetAllTCPv6ConnectionsAsync                         return Task Run     gt GetTCPConnections lt MIB TCP6ROW OWNER PID  MIB TCP6TABLE OWNER PID gt  AF INET6                       public static List lt MIB TCP6ROW OWNER PID gt  GetAllTCPv6Connections                         return GetTCPConnections lt MIB TCP6ROW OWNER PID  MIB TCP6TABLE OWNER PID gt  AF INET6                      private static List lt IPR gt  GetTCPConnections lt IPR  IPT gt  int ipVersion   IPR   Row Type  IPT   Table Type                       List lt IPR gt  result   null               IPR   tableRows   null              int buffSize   0               var dwNumEntriesField   typeof IPT  GetField  dwNumEntries                    how much memory do we need              uint ret   GetExtendedTcpTable IntPtr Zero  ref buffSize  true  ipVersion  TCP TABLE CLASS TCP TABLE OWNER PID ALL               IntPtr tcpTablePtr   Marshal AllocHGlobal buffSize                try                               ret   GetExtendedTcpTable tcpTablePtr  ref buffSize  true  ipVersion  TCP TABLE CLASS TCP TABLE OWNER PID ALL                   if  ret    0                      return new List lt IPR gt                         get the number of entries in the table                 IPT table    IPT Marshal PtrToStructure tcpTablePtr  typeof IPT                    int rowStructSize   Marshal SizeOf typeof IPR                    uint numEntries    uint dwNumEntriesField GetValue table                       buffer we will be returning                 tableRows   new IPR numEntries                    IntPtr rowPtr    IntPtr   long tcpTablePtr   4                   for  int i   0  i  lt  numEntries  i                                          IPR tcpRow    IPR Marshal PtrToStructure rowPtr  typeof IPR                        tableRows i    tcpRow                      rowPtr    IntPtr   long rowPtr   rowStructSize        next entry                                             finally                               result   tableRows  ToList      new List lt IPR gt                         Free the Memory                 Marshal FreeHGlobal tcpTablePtr                              return result                     public static string GetTcpStateName MIB TCP STATE state                        switch  state                                case MIB TCP STATE MIB TCP STATE CLOSED                      return  Closed                   case MIB TCP STATE MIB TCP STATE LISTEN                      return  Listen                   case MIB TCP STATE MIB TCP STATE SYN SENT                      return  SynSent                   case MIB TCP STATE MIB TCP STATE SYN RCVD                      return  SynReceived                   case MIB TCP STATE MIB TCP STATE ESTAB                      return  Established                   case MIB TCP STATE MIB TCP STATE FIN WAIT1                      return  FinWait 1                   case MIB TCP STATE MIB TCP STATE FIN WAIT2                      return  FinWait 2                   case MIB TCP STATE MIB TCP STATE CLOSE WAIT                      return  CloseWait                   case MIB TCP STATE MIB TCP STATE CLOSING                      return  Closing                   case MIB TCP STATE MIB TCP STATE LAST ACK                      return  LastAck                   case MIB TCP STATE MIB TCP STATE TIME WAIT                      return  TimeWait                   case MIB TCP STATE MIB TCP STATE DELETE TCB                      return  DeleteTCB                   default                      return   int state  ToString                                     private static readonly ConcurrentDictionary lt string  string gt  DicOfIpToHostName   new ConcurrentDictionary lt string  string gt              public const string UnknownHostName    Unknown                                                                                          public static string GetHostName IPAddress ipAddress                        return GetHostName ipAddress ToString                                                                                                      public static string GetHostName string ipAddress                        string hostName   null               if   DicOfIpToHostName TryGetValue ipAddress  out hostName                                 try                                       if  ipAddress     0 0 0 0     ipAddress                                                        hostName   ipAddress                                            else                                               hostName   Dns GetHostEntry ipAddress  HostName                                                          catch  Exception ex                                        Debug Print ex ToString                         hostName   UnknownHostName                                     DicOfIpToHostName ipAddress    hostName                             return hostName                                                                                                              lt summary gt              Will search for the an active NetworkInterafce that has a Gateway  otherwise             it will fallback to try from the DNS which is not safe               lt  summary gt               lt returns gt  lt  returns gt          public static NetworkInterface GetMainNetworkInterface                         List lt NetworkInterface gt  candidates   new List lt NetworkInterface gt                  if  NetworkInterface GetIsNetworkAvailable                                  NetworkInterface   NetworkInterfaces                       NetworkInterface GetAllNetworkInterfaces                     foreach                       NetworkInterface ni in NetworkInterfaces                                        if  ni OperationalStatus    OperationalStatus Up                          candidates Add ni                                                if  candidates Count    1                                return candidates 0                                 Accoring to our tech  the main NetworkInterface should have a Gateway                 and it should be the ony one with a gateway              if  candidates Count  gt  1                                for  int n   candidates Count - 1  n  gt   0  n--                                        if  candidates n  GetIPProperties   GatewayAddresses Count    0                                                candidates RemoveAt n                                                            if  candidates Count    1                                        return candidates 0                                                   Fallback to try by getting my ipAdress from the dns             IPAddress myMainIpAdress   null              IPHostEntry host   Dns GetHostEntry Dns GetHostName                 foreach  IPAddress ip in host AddressList                                if  ip AddressFamily    AddressFamily InterNetwork     Get the first IpV4                                       myMainIpAdress   ip                      break                                               if  myMainIpAdress    null                                NetworkInterface   NetworkInterfaces                       NetworkInterface GetAllNetworkInterfaces                     foreach  NetworkInterface ni in NetworkInterfaces                                        if  ni OperationalStatus    OperationalStatus Up                                                IPInterfaceProperties props   ni GetIPProperties                            foreach  UnicastIPAddressInformation ai in props UnicastAddresses                                                        if  ai Address Equals myMainIpAdress                                                                 return ni                                                                                                                             return null                                                                                                        lt summary gt              AddressFamily InterNetwork   IPv4             Thanks to Dr  Wilys Apprentice at             http   stackoverflow com questions 1069103 how-to-get-the-ip-address-of-the-server-on-which-my-c-sharp-application-is-runni             using System Net NetworkInformation               lt  summary gt               lt param name  mac  gt  lt  param gt               lt param name  addressFamily  gt AddressFamily InterNetwork   IPv4   AddressFamily InterNetworkV6   IPv6 lt  param gt               lt returns gt  lt  returns gt          public static IPAddress GetIpFromMac PhysicalAddress mac  AddressFamily addressFamily   AddressFamily InterNetwork                        NetworkInterface   NetworkInterfaces                   NetworkInterface GetAllNetworkInterfaces                 foreach  NetworkInterface ni in NetworkInterfaces                                if  ni GetPhysicalAddress   Equals mac                                         if  ni OperationalStatus    OperationalStatus Up                                                IPInterfaceProperties props   ni GetIPProperties                            foreach  UnicastIPAddressInformation ai in props UnicastAddresses                                                        if  ai DuplicateAddressDetectionState    DuplicateAddressDetectionState Preferred                                                                if  ai Address AddressFamily    addressFamily                                                                        return ai Address                                                                                                                                                               return null                                                                                                        lt summary gt              Return the best guess of main ipAdress  To get it in the form aaa bbb ccc ddd just call                 ToString          on the result               lt  summary gt               lt returns gt  lt  returns gt          public static IPAddress GetMyInternetIpAddress                         NetworkInterface ni   GetMainNetworkInterface                IPAddress ipAddress   GetIpFromMac ni GetPhysicalAddress                 if  ipAddress    null     could it be possible                                 ipAddress   GetIpFromMac ni GetPhysicalAddress    AddressFamily InterNetworkV6                              return ipAddress                                                                                                   public static bool IsBroadcastAddress IPAddress ipAddress                        if  ipAddress AddressFamily    AddressFamily InterNetwork                                return ipAddress GetAddressBytes   3     255                             if  ipAddress AddressFamily    AddressFamily InterNetworkV6                                return false     NO broadcast in IPv6                            return false                                                                                                   public static bool IsMulticastAddress IPAddress ipAddress                        if  ipAddress AddressFamily    AddressFamily InterNetwork                                   Source  https   technet microsoft com en-us library cc772041 v ws 10  aspx                 return ipAddress GetAddressBytes   0   gt   224  amp  amp  ipAddress GetAddressBytes   0   lt   239                             if  ipAddress AddressFamily    AddressFamily InterNetworkV6                                return ipAddress IsIPv6Multicast                             return false

User · Answer

If you want to avoid using DNS   List lt IPAddress gt  ipList   new List lt IPAddress gt     foreach  var netInterface in NetworkInterface GetAllNetworkInterfaces          foreach  var address in netInterface GetIPProperties   UnicastAddresses                if  address Address AddressFamily    AddressFamily InterNetwork                        Console WriteLine  found IP     address Address ToString                 ipList Add address Address

User · Answer

Here is how i solved it  i know if you have several physical interfaces this might not select the exact eth you want   private string FetchIP           Get all IP registered     List lt string gt  IPList   new List lt string gt         IPHostEntry host      host   Dns GetHostEntry Dns GetHostName         foreach  IPAddress ip in host AddressList                if  ip AddressFamily    AddressFamily InterNetwork                        IPList Add ip ToString                            Find the first IP which is not only local     foreach  string a in IPList                Ping p   new Ping            string   b   a Split               string ip2   b 0          b 1          b 2      1           PingReply t   p Send ip2           p Dispose            if  t Status    IPStatus Success  amp  amp  ip2    a                        return a                      return null

User · Answer

Cleaner and an all in one solution  D    This returns the first IP4 address or null return Dns GetHostEntry Dns GetHostName    AddressList FirstOrDefault ip   gt  ip AddressFamily    AddressFamily InterNetwork

User · Answer

WebClient webClient   new WebClient    string IP   webClient DownloadString  http   myip ozymo com

User · Answer

Don t rely on InterNetwork all the time because you can have more than one device which also uses IP4 which would screw up the results in getting your IP  Now  if you would like you may just copy this and please review it or update it to how you see fit   First I get the address of the router  gateway  If it comes back that I am connected to a gateway  which mean not connected directly into the modem wireless or not  then we have our gateway address as IPAddress else we a null pointer IPAddress reference   Then we need to get the computer s list of IPAddresses  This is where things are not that hard because routers  all routers  use 4 bytes        The first three are the most important because any computer connected to it will have the IP4 address matching the first three bytes  Ex  192 168 0 1 is standard for router default IP unless changed by the adminstrator of it   192 168 0  or whatever they may be is what we need to match up  And that is all I did in IsAddressOfGateway function   The reason for the length matching is because not all addresses  which are for the computer only  have the length of 4 bytes  If you type in netstat in the cmd  you will find this to be true  So there you have it  Yes  it takes a little more work to really get what you are looking for  Process of elimination  And for God s sake  do not find the address by pinging it which takes time because first you are sending the address to be pinged and then it has to send the result back  No  work directly with  Net classes which deal with your system environment and you will get the answers you are looking for when it has to solely do with your computer   Now if you are directly connected to your modem  the process is almost the same because the modem is your gateway but the submask is not the same because your getting the information directly from your DNS Server via modem and not masked by the router serving up the Internet to you although you still can use the same code because the last byte of the IP assigned to the modem is 1  So if IP sent from the modem which does change is 111 111 111 1  then you will get 111 111 111  some byte value   Keep in mind the we need to find the gateway information because there are more devices which deal with internet connectivity than your router and modem   Now you see why you DON T change your router s first two bytes 192 and 168  These are strictly distinguished for routers only and not internet use or we would have a serious issue with IP Protocol and double pinging resulting in crashing your computer  Image that your assigned router IP is 192 168 44 103 and you click on a site with that IP as well  OMG  Your computer would not know what to ping  Crash right there  To avoid this issue  only routers are assigned these and not for internet usage  So leave the first two bytes of the router alone   static IPAddress FindLanAddress         IPAddress gateway   FindGetGatewayAddress        if  gateway    null          return null       IPAddress   pIPAddress   Dns GetHostAddresses Dns GetHostName          foreach  IPAddress address in pIPAddress                       if  IsAddressOfGateway address  gateway                   return address      return null    static bool IsAddressOfGateway IPAddress address  IPAddress gateway        if  address    null  amp  amp  gateway    null          return IsAddressOfGateway address GetAddressBytes   gateway GetAddressBytes         return false    static bool IsAddressOfGateway byte   address  byte   gateway        if  address    null  amp  amp  gateway    null                int gwLen   gateway Length          if  gwLen  gt  0                        if  address Length    gateway Length                                --gwLen                  int counter   0                  for  int i   0  i  lt  gwLen  i                                          if  address i     gateway i                             counter                                    return  counter    gwLen                                     return false     static IPAddress FindGetGatewayAddress         IPGlobalProperties ipGlobProps   IPGlobalProperties GetIPGlobalProperties         foreach  NetworkInterface ni in NetworkInterface GetAllNetworkInterfaces                  IPInterfaceProperties ipInfProps   ni GetIPProperties            foreach  GatewayIPAddressInformation gi in ipInfProps GatewayAddresses              return gi Address            return null

User · Answer

Try this    IPAddress   localIPs   Dns GetHostAddresses Dns GetHostName      String MyIp   localIPs 0  ToString

User · Answer

Maybe by external IP you can consider  if you are in a Web server context  using this  Request ServerVariables  LOCAL ADDR      I was asking the same question as you and I found it in this stackoverflow article   It worked for me

User · Answer

To find IP address list I have used this solution  public static IEnumerable lt string gt  GetAddresses         var host   Dns GetHostEntry Dns GetHostName         return  from ip in host AddressList where ip AddressFamily    AddressFamily lo select ip ToString    ToList        But I personally like below solution to get local valid IP address   public static IPAddress GetIPAddress string hostName        Ping ping   new Ping        var replay   ping Send hostName        if  replay Status    IPStatus Success                return replay Address            return null      public static void Main         Console WriteLine  Local IP Address      GetIPAddress Dns GetHostName          Console WriteLine  Google IP     GetIPAddress  google com        Console ReadLine

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And this is to get all local IPs in csv format in VB NET  Imports System Net Imports System Net Sockets  Function GetIPAddress   As String     Dim ipList As List Of String    New List Of String      Dim host As IPHostEntry     Dim localIP As String           host   Dns GetHostEntry Dns GetHostName        For Each ip As IPAddress In host AddressList         If ip AddressFamily   AddressFamily InterNetwork Then             localIP   ip ToString               ipList Add localIP          End If     Next     Dim ret As String   String Join      ipList ToArray      Return ret End Function

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Nope  that is pretty much the best way to do it   As a machine could have several IP addresses you need to iterate the collection of them to find the proper one   Edit  The only thing I would change would be to change this   if  ip AddressFamily ToString       InterNetwork     to this   if  ip AddressFamily    AddressFamily InterNetwork    There is no need to ToString an enumeration for comparison

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namespace NKUtilities        using System      using System Net       public class DNSUtility               public static int Main  string    args                       String strHostName   new String                 if  args Length    0                               Getting Ip address of local machine                     First get the host name of local machine                strHostName   Dns GetHostName                   Console WriteLine   Local Machine s Host Name       strHostName                         else                           strHostName   args 0                             Then using host name  get the IP address list             IPHostEntry ipEntry   DNS GetHostByName  strHostName             IPAddress    addr   ipEntry AddressList             for  int i   0  i  lt  addr Length  i                              Console WriteLine   IP Address  0    1     i  addr i  ToString                            return 0

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If you are running in intranet you ll be able to get local machine IP address and if not you ll get external ip address with this  Web     this will bring the IP for the current machine on browser System Web HttpContext Current Request UserHostAddress   Desktop     This one will bring all local IPs for the desired namespace IPAddress   localIPs   Dns GetHostAddresses Dns GetHostName

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using System Net   string host   Dns GetHostName    IPHostEntry ip   Dns GetHostEntry host   Console WriteLine ip AddressList 0  ToString       Just tested this on my machine and it works

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For getting the current public IP address  all you need to do is create an ASPX page with the following line on the page load event   Response Write HttpContext Current Request UserHostAddress ToString

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Yet another way to get your public IP address is to use OpenDNS s resolve1 opendns com server with myip opendns com as the request   On the command line this is     nslookup myip opendns com resolver1 opendns com   Or in C  using the DNSClient nuget     var lookup   new LookupClient new IPAddress new byte     208  67  222  222        var result   lookup Query  myip opendns com   QueryType ANY     This is a bit cleaner than hitting http endpoints and parsing responses

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Get all IP addresses as strings using LINQ   using System Linq  using System Net NetworkInformation  using System Net Sockets      string   allIpAddresses   NetworkInterface GetAllNetworkInterfaces        SelectMany c  gt c GetIPProperties   UnicastAddresses          Where d  gt d Address AddressFamily    AddressFamily InterNetwork           Select d  gt d Address ToString          ToArray      TO FILTER OUT PRIVATE ONES     First  define an extension method IsPrivate     public static class IPAddressExtensions          Collection of private CIDRs  IpAddress Mask       private static Tuple lt int  int gt     privateCidrs   new     10 0 0 0 8    172 16 0 0 12    192 168 0 0 16            Select c  gt Tuple Create BitConverter ToInt32 IPAddress                                      Parse c Split      0   GetAddressBytes    0                                  IPAddress HostToNetworkOrder -1  lt  lt   32-int Parse c Split      1                ToArray        public static bool IsPrivate this IPAddress ipAddress                int ip   BitConverter ToInt32 ipAddress GetAddressBytes    0           return  privateCidrs Any cidr  gt  ip  amp  cidr Item2    cidr Item1  amp  cidr Item2                             And then use it to filter out private IPs   string   publicIpAddresses   NetworkInterface GetAllNetworkInterfaces        SelectMany c  gt c GetIPProperties   UnicastAddresses          Where d  gt d Address AddressFamily    AddressFamily InterNetwork              amp  amp   d Address IsPrivate      Filter out private ones                    Select d  gt d Address ToString          ToArray

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The question doesn t say ASP NET MVC but I m just leaving this here anyway   Request UserHostAddress

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The LINQ solution   Dns GetHostEntry Dns GetHostName    AddressList Where ip   gt  ip AddressFamily    AddressFamily InterNetwork  Select ip   gt  ip ToString    FirstOrDefault

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I just thought that I would add my own  one-liner  even though there are many other useful answers already      string ipAddress   new WebClient   DownloadString  http   icanhazip com

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return Dns GetHostEntry Dns GetHostName    AddressList FirstOrDefault ip   gt  ip AddressFamily    AddressFamily InterNetwork     Simple single line of code that returns the first internal IPV4 address or null if there are none  Added as a comment above  but may be useful to someone  some solutions above will return multiple addresses that need further filtering    It s also easy to return loopback instead of null I guess with   return Dns GetHostEntry Dns GetHostName    AddressList FirstOrDefault ip   gt  ip AddressFamily    AddressFamily InterNetwork     new IPAddress  new byte    127  0  0  1

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