How do I re-bind a socket in MacOSX/Ubuntu? A second time

Question

I have the following code:

if ( ( m_mainSocket = ::socket( PF_INET, SOCK_STREAM, IPPROTO_TCP ) ) < 0 )
{
    throw Exception( __FILE__, __LINE__ ) << "Unable to create socket";
}

int on( 0 );

if ( setsockopt( m_mainSocket, SOL_SOCKET, SO_REUSEADDR, &on, sizeof( on ) ) )
{
    throw Exception( __FILE__, __LINE__ ) << "Can't make server socket resusable.";
}

sockaddr_in addr;
memset( &addr, 0, sizeof( addr ) );

addr.sin_family = AF_INET;
addr.sin_addr.s_addr = htonl( INADDR_ANY );
addr.sin_port = htons( p_localPort );

if ( ::bind( m_mainSocket, reinterpret_cast< sockaddr * >( &addr ), sizeof( addr ) ) < 0 )
{
    throw Exception( __FILE__, __LINE__ ) << "Failed to bind the server socket";
}

When I CLOSE the server, with close(), of couse, I can't open the server again in the same port. Why? I need to change the port OR reboot the system. It happens only in Ubuntu AND MacOSX. In Windows I don't have this problem.

The error happend in the ::bind() function. It doesn't allow me to re-bind() a socket twice.

How do I re-bind?

Answer 1

You need to pass 1, not 0, to REUSEADDR.

From the socket(7) man page:

   Socket Options
       These socket options can be set by using setsockopt(2)  and  read  with
       getsockopt(2) with the socket level set to SOL_SOCKET for all sockets:

      ....

       SO_REUSEADDR
              Indicates  that  the rules used in validating addresses supplied
              in a bind(2) call should allow reuse of  local  addresses.   For
              AF_INET  sockets  this means that a socket may bind, except when
              there is an active listening socket bound to the address.   When
              the listening socket is bound to INADDR_ANY with a specific port
              then it is not possible to bind  to  this  port  for  any  local
              address.  Argument is an integer boolean flag.