PRB: WSAStartup() May Return WSAVERNOTSUPPORTED on Second Call

• Microsoft Windows Software Development Kit (SDK) for Windows version 3.1
• Microsoft Win32 Software Development Kit (SDK) versions 3.1, 3.5, 3.51, and 4.0

SYMPTOMS

If two sections of code within the same process call WSAStartup(), the second call to WSAStartup() fails and returns error WSAVERNOTSUPPORTED unless the second call specifies the version negotiated in the first call.

This happens even if the requested version would normally be accepted. Often the extra calls to WSAStartup() come from one or more DLLs loaded by the process.

RESOLUTION

If multiple calls are made to WSAStartup(), the second call must request the same version negotiated in the first call.

MORE INFORMATION

Some specific examples may help. Currently, if the version of Winsock requested is 1.1 or greater, the negotiated version will be 1.1. If a version less than 1.1 is requested, the call fails and returns the WSAVERNOTSUPPORTED error.

Example One

First call : 1.1 requested Second call: 1.1 requested

Result     : Success

Example Two

First call : 2.0 requested Second call: 1.1 requested

Result     : Success

Example Three

First call : 2.0 requested Second call: 2.0 requested

Result     : WSAVERNOTSUPPORTED

Example Four

First call : 1.1 requested Second call: 2.0 requested

Result     : WSAVERNOTSUPPORTED