The WSAEnumProtocols function retrieves information about available transport protocols.

Syntax

int WSAEnumProtocols(
  __in     LPINT lpiProtocols,
  __out    LPWSAPROTOCOL_INFO lpProtocolBuffer,
  __inout  LPDWORD lpdwBufferLength
);

Parameters

lpiProtocols [in]

Null-terminated array of iProtocol values. This parameter is optional; if lpiProtocols is NULL, information on all available protocols is returned. Otherwise, information is retrieved only for those protocols listed in the array.

lpProtocolBuffer [out]

Buffer that is filled with WSAPROTOCOL_INFO structures.

lpdwBufferLength [in, out]

On input, number of bytes in the lpProtocolBuffer buffer passed to WSAEnumProtocols. On output, the minimum buffer size that can be passed to WSAEnumProtocols to retrieve all the requested information. This routine has no ability to enumerate over multiple calls; the passed-in buffer must be large enough to hold all entries in order for the routine to succeed. This reduces the complexity of the API and should not pose a problem because the number of protocols loaded on a computer is typically small.

Return Value

If no error occurs, WSAEnumProtocols returns the number of protocols to be reported. Otherwise, a value of SOCKET_ERROR is returned and a specific error code can be retrieved by calling WSAGetLastError.

Remarks

The WSAEnumProtocols function is used to discover information about the collection of transport protocols and protocol chains installed on the local computer. Since layered protocols are only usable by applications when installed in protocol chains, information on layered protocols is not included in lpProtocolBuffer. The lpiProtocols parameter can be used as a filter to constrain the amount of information provided. Often, lpiProtocols will be specified as a NULL pointer that will cause the function to return information on all available transport protocols and protocol chains.

A WSAPROTOCOL_INFO structure is provided in the buffer pointed to by lpProtocolBuffer for each requested protocol. If the specified buffer is not large enough (as indicated by the input value of lpdwBufferLength ), the value pointed to by lpdwBufferLength will be updated to indicate the required buffer size. The application should then obtain a large enough buffer and call WSAEnumProtocols again.

The order in which the WSAPROTOCOL_INFO structures appear in the buffer coincides with the order in which the protocol entries were registered by the service provider using the WS2_32.DLL, or with any subsequent reordering that occurred through the Windows Sockets application or DLL supplied for establishing default TCP/IP providers.

Requirements

See Also

Winsock Reference

Winsock Functions

WSAPROTOCOL_INFO

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Build date: 10/29/2009