Re: socket bind always returns 0, why?

Wed, 28 May 2014 08:11:02 -0700 (PDT)
Thanks, I've changed it to LOOPBACK, but it didn't change anything. I still see two bindings in netstat:
[./]$ sudo netstat -lptu |grep 1908
tcp 0 0 localhost:19080 *:* LISTEN 12273/Test
tcp 0 0 localhost:19080 *:* LISTEN 12273/Test

On Tuesday, May 27, 2014 7:45:32 PM UTC-5, Geoff wrote:

On Tue, 27 May 2014 10:27:58 -0700 (PDT), wrote:

The following code returns 0 from the bind, even when netstat clearly shows that the port is taken by another process, ie the following function will always return true. Why?

bool isPortAvailable( int port )


           SOCKET candidateSocket;

           if(( candidateSocket = socket( AF_INET, SOCK_STREAM, 0 )) == -1 )

               return false;

           struct sockaddr_in serverAddress;

           memset (&serverAddress, 0, sizeof (serverAddress));

           serverAddress.sin_family = AF_INET;

           serverAddress.sin_addr.s_addr = htonl( INADDR_ANY );

           serverAddress.sin_port = htons( port );

           if( ::bind( candidateSocket, (struct sockaddr*)&serverAddress, sizeof( serverAddress )) != 0 )


               closesocket( candidateSocket );

               return false;


           closesocket( candidateSocket );

           return true;


My first guess would be that the other process has the port on a

distinct IP address, your bind is to INADDR_ANY. This would let your

process have a port listening on which, IIRC, is distinct

from another process listening on for example. To prove

this guess correct, use the same IP address to which the other process

is bound and see if this function fails.

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