Sending and receiving data over a network using TcpClient

Question

I need to develop a service that will connect to a TCP server  Main tasks are reading incoming messages and also sending commands to the server in ten minutes  like a synchronize command  For example  I used the TcpClient object as shown below       TcpClient tcpClient   new TcpClient    tcpClient Connect  x x x x   9999   networkStream   tcpClient GetStream    clientStreamReader   new StreamReader networkStream   clientStreamWriter   new  StreamWriter networkStream   while true       clientStreamReader Read       Also  when I need to write out something in any method  I use    clientStreamWriter write  xxx      Is this usage correct  Or is there a better way

User · Answer

First of all  TCP does not guarantee that everything that you send will be received with the same read at the other end  It only guarantees that all bytes that you send will arrive and in the correct order   Therefore  you will need to keep building up a buffer when reading from the stream  You will also have to know how large each message is   The simplest ever is to use a non-typeable ASCII character to mark the end of the packet and look for it in the received data

User · Answer

First  I recommend that you use WCF   NET Remoting  or some other higher-level communication abstraction  The learning curve for  simple  sockets is nearly as high as WCF  because there are so many non-obvious pitfalls when using TCP IP directly   If you decide to continue down the TCP IP path  then review my  NET TCP IP FAQ  particularly the sections on message framing and application protocol specifications   Also  use asynchronous socket APIs  The synchronous APIs do not scale and in some error situations may cause deadlocks  The synchronous APIs make for pretty little example code  but real-world production-quality code uses the asynchronous APIs

User · Answer

Be warned - this is a very old and cumbersome  solution    By the way  you can use serialization technology to send strings  numbers or any objects which are support serialization  most of  NET data-storing classes  amp  structs are  Serializable    There  you should at first send Int32-length in four bytes to the stream and then send binary-serialized  System Runtime Serialization Formatters Binary BinaryFormatter  data into it   On the other side or the connection  on both sides actually  you definetly should have a byte   buffer which u will append and trim-left at runtime when data is coming    Something like that I am using   namespace System Net Sockets       public class TcpConnection   IDisposable               public event EvHandler lt TcpConnection  DataArrivedEventArgs gt  DataArrive   delegate              public event EvHandler lt TcpConnection gt  Drop   delegate               private const int IntSize   4          private const int BufferSize   8   1024           private static readonly SynchronizationContext  syncContext   SynchronizationContext Current          private readonly TcpClient  tcpClient          private readonly object  droppedRoot   new object            private bool  dropped          private byte    incomingData   new byte 0           private Nullable lt int gt   objectDataLength           public TcpClient TcpClient   get   return  tcpClient              public bool Dropped   get   return  dropped               private void DropConnection                         lock   droppedRoot                                if  Dropped                      return                    dropped   true                              tcpClient Close                 syncContext Post delegate   Drop this      null                      public void SendData PCmds pCmd    SendDataInternal new object     pCmd               public void SendData PCmds pCmd  object   datas                        datas ThrowIfNull                SendDataInternal new object     pCmd   Append datas                      private void SendDataInternal object data                        if  Dropped                  return               byte   bytedata               using  MemoryStream ms   new MemoryStream                                  BinaryFormatter bf   new BinaryFormatter                     try   bf Serialize ms  data                     catch   return                     bytedata   ms ToArray                               try                               lock   tcpClient                                        TcpClient Client BeginSend BitConverter GetBytes bytedata Length   0  IntSize  SocketFlags None  EndSend  null                       TcpClient Client BeginSend bytedata  0  bytedata Length  SocketFlags None  EndSend  null                                               catch   DropConnection                        private void EndSend IAsyncResult ar                        try   TcpClient Client EndSend ar                 catch                        public TcpConnection TcpClient tcpClient                         tcpClient   tcpClient              StartReceive                       private void StartReceive                         byte   buffer   new byte BufferSize                try                                tcpClient Client BeginReceive buffer  0  buffer Length  SocketFlags None  DataReceived  buffer                             catch   DropConnection                         private void DataReceived IAsyncResult ar                        if  Dropped                  return               int dataRead               try   dataRead   TcpClient Client EndReceive ar                 catch                               DropConnection                    return                             if  dataRead    0                                DropConnection                    return                             byte   byteData   ar AsyncState as byte                 incomingData    incomingData Append byteData Take dataRead  ToArray                 bool exitWhile   false               while  exitWhile                                exitWhile   true                   if   objectDataLength HasValue                                        if   incomingData Length  gt    objectDataLength Value                                                object data                          BinaryFormatter bf   new BinaryFormatter                             using  MemoryStream ms   new MemoryStream  incomingData  0   objectDataLength Value                               try   data   bf Deserialize ms                                 catch                                                               SendData PCmds Disconnect                                   DropConnection                                    return                                                          syncContext Post delegate object T                                                        try   DataArrive this  new DataArrivedEventArgs T                                  catch   DropConnection                                 data                             incomingData    incomingData TrimLeft  objectDataLength Value                            objectDataLength   null                          exitWhile   false                                                          else                     if   incomingData Length  gt   IntSize                                                 objectDataLength   BitConverter ToInt32  incomingData TakeLeft IntSize   0                            incomingData    incomingData TrimLeft IntSize                           exitWhile   false                                                  StartReceive                        public void Dispose     DropConnection                That is just an example  you should edit it for your use

User · Answer

I have had luck using the socket object directly  rather than the TCP client    I create a Server object that looks something like this  I ve edited some stuff such as exception handling out for brevity  but I hope that the idea comes across       public class Server         private Socket sock         You ll probably want to initialize the port and address in the        constructor  or via accessors  but to start your server listening        on port 8080 and on any IP address available on the machine        private int port   8080      private IPAddress addr   IPAddress Any          This is the method that starts the server listening      public void Start                    Create the new socket on which we ll be listening          this sock   new Socket              addr AddressFamily              SocketType Stream              ProtocolType Tcp              Bind the socket to the address and port          sock Bind new IPEndPoint this addr  this port               Start listening          this sock Listen this backlog              Set up the callback to be notified when somebody requests            a new connection          this sock BeginAccept this OnConnectRequest  sock                 This is the method that is called when the socket recives a request        for a new connection      private void OnConnectRequest IAsyncResult result                   Get the socket  which should be this listener s socket  from            the argument          Socket sock    Socket result AsyncState             Create a new client connection  using the primary socket to            spawn a new socket          Connection newConn   new Connection sock EndAccept result               Tell the listener socket to start listening again          sock BeginAccept this OnConnectRequest  sock             Then  I use a separate Connection class to manage the individual connection with the remote host   That looks something like this     public class Connection         private Socket sock         Pick whatever encoding works best for you   Just make sure the remote         host is using the same encoding      private Encoding encoding   Encoding UTF8       public Connection Socket s                this sock   s             Start listening for incoming data    If you want a multi-            threaded service  you can start this method up in a separate            thread           this BeginReceive                  Call this method to set this connection s socket up to receive data      private void BeginReceive                 this sock BeginReceive                  this dataRcvBuf  0                  this dataRcvBuf Length                  SocketFlags None                  new AsyncCallback this OnBytesReceived                   this                 This is the method that is called whenever the socket receives        incoming bytes      protected void OnBytesReceived IAsyncResult result                   End the data receiving that the socket has done and get            the number of bytes read          int nBytesRec   this sock EndReceive result              If no bytes were received  the connection is closed  at            least as far as we re concerned           if  nBytesRec  lt   0                        this sock Close                return                       Convert the data we have to a string          string strReceived   this encoding GetString              this dataRcvBuf  0  nBytesRec                  Now  do whatever works best with the string data             You could  for example  look at each character in the string            one-at-a-time and check for characters like the  end of text             character    u0003   from a client indicating that they ve finished            sending the current message   It s totally up to you how you want            the protocol to work              Whenever you decide the connection should be closed  call             sock Close   and don t call sock BeginReceive   again   But as long             as you want to keep processing incoming data                Set up again to get the next chunk of data          this sock BeginReceive              this dataRcvBuf  0              this dataRcvBuf Length              SocketFlags None              new AsyncCallback this OnBytesReceived               this              You can use your Connection object to send data by calling its Socket directly  like so     this sock Send this encoding GetBytes  Hello to you  remote host        As I said  I ve tried to edit the code here for posting  so I apologize if there are any errors in it

User · Answer

I ve developed a dotnet library that might come in useful  I have fixed the problem of never getting all of the data if it exceeds the buffer  which many posts have discounted  Still some problems with the solution but works descently well https   github com NicholasLKSharp DotNet-TCP-Communication

[c#] Sending and receiving data over a network using TcpClient

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