The socket call sets options associated with a socket.
Syntax
#include <types.h> #include <sys\socket.h> int setsockopt(s, level, optname, optval, optlen) int s; int level; int optname; char *optval; int optlen;
Parameters
s
Description
This call provides an application program with the means to control a socket communication. The setsockopt() call can be used to set options associated with a socket, such as enabling debugging at the socket or protocol level, controlling timeouts, or permitting socket data broadcasts. Options can exist at the socket or the protocol level; options are always present at the highest socket level. When setting socket options, the level of the option and the name of the option must be specified. The following table lists the supported levels:
Supported Levels
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The optval and optlen parameters are used to pass data used by the particular set command. The optval parameter points to a buffer containing the data needed by the set command. The optval parameter is optional and if data is not needed by the command, can be set to the NULL pointer. The optlen parameter must be set to the size of the data or data type pointed to by optval. For socket options that are toggles, the option is enabled if optval is nonzero and disabled if optval is 0.
The following tables list the supported options for setsockopt() at each level (SOL_SOCKET, IPPROTO_IP, IPPROTO_TCP). Detailed descriptions of the options follow each table.
Supported setsockopt() Socket Options for SOL_SOCKET
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Table Note (*) This column specifies the communication domains to which this option applies: I for internet, L for Local IPC, and N for NetBIOS.
The following options are recognized for SOL_SOCKET:
Option
The optval parameter points to a linger structure, defined in <SYS\SOCKET.H>:
Field
The l_linger field specifies the amount of time in seconds to linger on close. A value of zero will cause soclose() to wait until the disconnect completes.
When this option is enabled, it causes out-of-band data to be placed in the normal data input queue as it is received, making it available to recv(), and recvfrom(), without having to specify the MSG_OOB flag in those calls. When this option is disabled, it causes out-of-band data to be placed in the priority data input queue as it is received, making it available to recv() and recvfrom() only by specifying the MSG_OOB flag in those calls.
Use inetcfg -g tcprwinsize to see the default and maximum receive socket buffer sizes for stream (TCP) sockets or raw sockets. Use inetcfg -g udprwinsize to see the default and maximum receive socket buffer sizes for UDP sockets.
Multicast applications must set this socket option if they want to join the same Class D IP address and port for sending and receiving multicast packets.
Use inetcfg -g tcpswinsize to see the default and maximum send socket buffer sizes for stream (TCP) sockets or raw sockets. Use inetcfg -g udpswinsize to see the default and maximum send socket buffer sizes for UDP sockets.
Supported setsockopt() Socket Options for IPPROTO_IP
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The following options are recognized for IPPROTO_IP:
Option
Supported setsockopt() Socket Options for IPPROTO_TCP
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The following options are recognized for IPPROTO_TCP:
Option
Supported setsockopt() Socket Options for NBPROTO_NB
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The following option is recognized for NBPROTO_NB:
Option
NB_DGRAM
Return Values
The value 0 indicates success; the value -1 indicates an error. You can get the specific error code by calling sock_errno() or psock_errno().
sock_errno() Value
Examples
The following are examples of the setsockopt() call. See getsockopt() for examples of how the options are queried.
int rc;int s; int optval; struct linger lstruct; /* extracted from sys/socket.h */ int setsockopt(int s, int level, int optname, char *optval, int optlen); ... /* I want out of band data in the normal input queue */ optval = 1; rc = setsockopt(s, SOL_SOCKET, SO_OOBINLINE, (char *) &optval, sizeof(int)); ... /* I want to linger on close */ lstruct.l_onoff = 1; lstruct.l_linger = 100; rc = setsockopt(s, SOL_SOCKET, SO_LINGER, (char *) &lstruct, sizeof(lstruct));
Related Calls
bind()
endprotoent()
getprotobyname()
getprotobynumber()
getprotoent()
getsockopt()
ioctl()
setprotoent()
sock_errno()
socket()