getsockopt

getsockopt retrieves the value of the specified option for a socket.

Syntax

int getsockopt(
    SOCKET s,
    int level,
    int optname,
    char *optval,
    int *optlen
);

Parameters

s

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

level

A network layer. The values for this parameter are defined under setsockopt.

optname

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

optval

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

optlen

A size, in bytes, of the buffer at optval. Upon return, it contains the size of the option value retrieved, 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.

Use WSAGetLastError to retrieve a specific error code.

Remarks

Some values for the optname parameter are not supported. The following sections list the options, by socket type, that are supported.

SOL_SOCKET level options:

• SO_ACCEPTCONN

• SO_RCVBUF
• SO_SNDBUF
• SO_SND_DGRAMS (see Custom eRTOS socket options below)
• SO_RCV_DGRAMS (see Custom eRTOS 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 eRTOS socket options below)
• TCP_ACKNSEG (see Custom eRTOS socket options below)
• TCP_ACKDELAYTIME (see Custom eRTOS socket options below)

IPPROTO_IP level options:

• 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 eRTOS socket options: