Can someone help me out with this error

Any ideas?

system.net.sockets.socketexception only one usage of each socket address (protocol/network address/port) is normally permitted.
at system,net.sockets.socket.dobind(endpoint endpointsnapshot,socketaddress socket address)
followed by socket.bind (endpoint localep)
Tcplistener.start(int32 backlog)
Tcplistener.start()
at filerservermodule.fileserverform.listen()

Thanks