getsockopt

getsockopt retrieves an option associated with the specified socket.

Syntax

int getsockopt(
    [in]        SOCKET s,
    [in]        int level,
    [in]        int optname,
    [out]       char *optval,
    [in, out]   int *optlen
);

Parameters

[in] s

The socket descriptor of a currently open socket that uses the IP protocol.

[in] level

The network layer. The values for this parameter are defined in setsockopt.

[in] optname

The socket information type to be returned. Some values for the optname parameter are not supported. See the Remarks section below.

[out] optval

A pointer to a buffer to receive the option value. Its proper length depends on the information type specified in optname being returned.

[in, out] optlen

A pointer to the size, in bytes, of the buffer at optval. Upon return, it contains the size of the retrieved option value and may be less than the value passed in.

Return Value

If the function succeeds, it returns 0 (zero). If the function fails, it returns SOCKET_ERROR. Call WSAGetLastError to retrieve a specific error code.

Remarks

Some values for the optname parameter are not supported. The following section lists the supported options by socket type.

SOL_SOCKET level options:

• SO_ACCEPTCONN
• SO_RCVBUF
• SO_SNDBUF
• SO_SND_DGRAMS (see Custom wRTOS socket options below)
• SO_RCV_DGRAMS (see Custom wRTOS socket options below)
• SO_BROADCAST
• SO_KEEPALIVE
• SO_LINGER
• SO_REUSEADDR
• SO_OOBINLINE

IPPROTO_TCP level options:

• TCP_NODELAY
• TCP_MAXRT
• TCP_PROVIDE_TIMESTAMPS (see Custom wRTOS socket options below)
• TCP_ACKNSEG (see Custom wRTOS socket options below)
• TCP_ACKDELAYTIME (see Custom wRTOS socket options below)

IPPROTO_IP level options:

• IP_DONTFRAGMENT
• IP_HDRINCL
• IP_TTL
• IP_TOS
• IP_MULTICAST_IF
• IP_MULTICAST_TTL

IPPROTO_IPV6 level options:

• IPV6_HDRINCL
• IPV6_V6ONLY
• IPV6_UNICAST_HOPS
• IPV6_MULTICAST_IF
• IPV6_MULTICAST_HOPS
• IPV6_MULTICAST_LOOP

Note: None of the options for the IPPROTO_RM, NSPROTO_IPX, SOL_APPLETALK, and SOL_IRLMP socket types are supported.

Custom wRTOS socket options:

Requirements