WSAEADDRINUSE - Error 10048

Question/Problem: WSAEADDRINUSE (10048) Address already in use.

Answer/Solution:  Only one usage of each address is normally permitted.

WinSock description:  The "address" they refer to, typically refers to the local "socket name", which is made up of the 3-tuple: protocol, port-number and IP address.

User suggestions: Two of the same types of server applications cannot use the same port on the same machine. For instance, this error will occur if you try to run two applications that have FTP servers that both try to accept connections on port 21 (the standard FTP port). In this case, the 2nd application will fail with WSAEADDRINUSE.