Windows Sockets 2 Error Codes

This section provides a comprehensive list of error codes that can be returned by Windows Sockets 2 API functions. Understanding these codes is crucial for diagnosing and resolving network-related issues in Windows applications.

Common Error Codes

WSAEINTR (10004) A blocking operation was interrupted by a call to WSACancelAsyncRequest.
WSAEBADF (10009) A file descriptor or handle is invalid.
WSAEACCES (10013) An attempt was made to access a socket in a way forbidden by its access permissions.
WSAEFAULT (10014) Bad address. The system detected an invalid pointer address in attempting to use a pointer to a block of memory.
WSAEINVAL (10022) An invalid argument was supplied.
WSAEMFILE (10024) Too many open sockets.
WSAEWOULDBLOCK (10035) A non-blocking socket operation could not be completed immediately.
WSAEINPROGRESS (10036) A blocking Winsock 1.1 operation is in progress, or the service provider is still processing a callback function.
WSAENOTSOCK (10038) An operation was attempted on something that is not a socket.
WSAEADDRINUSE (10048) A requested address is already in use.
WSAECONNRESET (10054) An existing connection was forcibly closed by the remote host.
WSAETIMEDOUT (10060) A connection attempt failed because the connected party did not properly respond after a period of time.
WSAECONNABORTED (10053) An established connection was aborted due to error or failure on the host machine.
WSAECONNREFUSED (10061) A connection attempt failed because the connected party did not respond.
WSAENETDOWN (10050) The network subsystem failed.
WSAENETUNREACH (10051) A socket operation attempted to use an unreachable network.
WSAHOST_NOT_FOUND (11001) A DNS query failed to return a valid answer. Host not found.
WSATRY_AGAIN (11002) A temporary failure in name resolution occurred. Try again later.
WSANO_RECOVERY (11003) A nonrecoverable error occurred during name resolution.

Retrieving Error Codes

To retrieve the last error code for a Winsock function, use the WSAGetLastError() function. This function should be called immediately after a Winsock function returns an error.


#include <winsock2.h>
#include <stdio.h>

// ... inside a function after a Winsock call ...
int result = socket(...);
if (result == INVALID_SOCKET) {
    int errorCode = WSAGetLastError();
    fprintf(stderr, "Socket creation failed with error code: %d\n", errorCode);
    // You can then look up the error code in this documentation.
}

Error Code Categories

Winsock error codes can be broadly categorized:

Operation Interruption/Completion: Errors like WSAEINTR and WSAEWOULDBLOCK indicate issues with the timing or blocking nature of operations.
Access and Permissions: Codes such as WSAEACCES and WSAENOTSOCK relate to incorrect usage or permissions of socket resources.
Address and Connection Issues: Errors like WSAEADDRINUSE, WSAECONNREFUSED, and WSAETIMEDOUT point to problems with network addresses, connection establishment, or active connections.
Network State: Codes like WSAENETDOWN and WSAENETUNREACH reflect issues with the underlying network infrastructure.
Name Resolution: Errors like WSAHOST_NOT_FOUND and WSATRY_AGAIN are related to Domain Name System (DNS) lookups.