Bind failed Address already in use

Question

I am attempting to bind a socket to a port below     if  bind socket desc  struct sockaddr     amp server  sizeof server    lt  0        perror  bind failed  Error        return 1    puts  bind done      But it gives       serve    Socket created     bind failed  Error  Address already in use   Why does this error occur

User · Answer

I was also facing that problem  but I resolved it  Make sure that both the programs for client-side and server-side are on different projects in your IDE  in my case NetBeans  Then assuming you re using localhost  I recommend you to implement both the programs as two different projects

User · Answer

The error usually means that the port you are trying to open is being already used by another application  Try using netstat to see which ports are open and then use an available port   Also check if you are binding to the right ip address  I am assuming it would be localhost

User · Answer

You have a process that is already using that port  netstat -tulpn will enable one to find the process ID of that is using a particular port

User · Answer

As mentioned above the port is in use already  This could be due to several reasons    some other application is already using it   The port is in close wait state when your program is waiting for the other end to close the program refer  https   unix stackexchange com questions 10106 orphaned-connections-in-close-wait-state   The program might be in time wait state  you can wait or use socket option SO REUSEADDR as mentioned in another post    Do netstat -a   grep  lt portno gt  to check the port state

User · Answer

It also happens when you have not give enough permissions read and write  to your sock file   Just add expected permission to your sock contained folder and your sock file    chmod ug rw  path to your   chmod ug rw  path to your file sock   Then have fun

User · Answer

Address already in use means that the port you are trying to allocate for your current execution is already occupied allocated to some other process      If you are a developer and if you are working on an application which require lots of testing  you might have an instance of your same application running in background  may be you forgot to stop it properly    So if you encounter this error  just see which application process is using the port   In linux try using netstat -tulpn  This command will list down a process list with all running processes    Check if an application is using your port  If that application or process is another important one then you might want to use another port which is not used by any process application   Anyway you can stop the process which uses your port and let your application take it   If you are in linux environment try    Use netstat -tulpn to display the processes kill  lt pid gt  This will terminate the process   If you are using windows    Use netstat -a -o -n to check for the port usages Use taskkill  F  PID  lt pid gt  to kill that process

User · Answer

Everyone is correct  However  if you re also busy testing your code your own application might still  own  the socket if it starts and stops relatively quickly  Try SO REUSEADDR as a socket option      What exactly does SO REUSEADDR do       This socket option tells the kernel that even if this port is busy  in     the TIME WAIT state   go ahead and reuse it anyway   If it is busy      but with another state  you will still get an address already in use     error   It is useful if your server has been shut down  and then     restarted right away while sockets are still active on its port   You     should be aware that if any unexpected data comes in  it may confuse     your server  but while this is possible  it is not likely       It has been pointed out that  A socket is a 5 tuple  proto  local     addr  local port  remote addr  remote port    SO REUSEADDR just says     that you can reuse local addresses   The 5 tuple still must be     unique   by Michael Hunter  mphunter qnx com    This is true  and this     is why it is very unlikely that unexpected data will ever be seen by     your server   The danger is that such a 5 tuple is still floating     around on the net  and while it is bouncing around  a new connection     from the same client  on the same system  happens to get the same     remote port   This is explained by Richard Stevens in   2 7 Please     explain the TIME WAIT state

[c] Bind failed: Address already in use

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