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Sets options on a socket.The $QIO equivalent is the IO$_SETMODE or IO$_SETCHAR function.
#include <types.h>
#include <socket.h>
int setsockopt (int s, int level, int optname, char *optval, int optlen);
s
A socket descriptor created by socket().level
The protocol level for which the socket options are to be modified. It can have one of the following values:
SOL_SOCKET Set the options at the socket level. p Any protocol number. Set the options for protocol level p. See the <in.h> header file for the various IPPROTO values. optname
Interpreted by the protocol specified in level. Options at each protocol level are documented with the protocol.Table 6-3 lists the options available at the socket level.
Table 6-3 Socket Options Socket Option Description SO_BROADCAST Permits the sending of broadcast messages. Takes an integer parameter and requires a system user identification code (UIC) or SYSPRV, BYPASS, or OPER privilege. Optional for connectionless datagram. SO_DONTROUTE Indicates that outgoing messages should bypass the standard routing facilities. Instead, the messages are directed to the appropriate network interface according to the network portion of the destination address. SO_ERROR Obtains the socket error status and clears the error on the socket. TCPIP$C_FULL_DUPLEX_CLOSE When set before a close operation, both receive and transmit sides of the communications are closed. SO_KEEPALIVE Keeps connections active. Enables the periodic transmission of messages on a connected socket. If the connected socket fails to respond to the messages, the connection is broken. SO_LINGER Lingers on a close() function if data is present. Controls the action taken when unsent messages queue on a socket and a close() function is performed. Uses a linger structure parameter defined in <socket.h> to specify the state of the option and linger interval. If SO_LINGER is specified, the system blocks the process during the close() function until it can transmit the data or until the time expires. If the option is not specified and a close() function is issued, the system allows the process to continue as quickly as possible.
SO_OOBINLINE Leaves the received out-of-band (OOB) data (data marked urgent) in line. Takes an integer parameter. SO_RCVBUF Sets the receive buffer size. Takes an integer parameter and requires a system UIC or SYSPRV, BYPASS, or OPER privilege. SO_RCVTIMEO For Compaq use only. Sets the timeout value for a recv() operation. SO_REUSEADDR Specifies that the rules used in validating addresses supplied by a bind() function should allow reuse of local addresses. Takes an integer value. SO_REUSEPORT Allows more than one process to receive UDP datagrams destined for the same port. The bind() call that binds a process to the port must be preceded by a setsockopt() call specifying this option. SO_SHARE Allows multiple processes to share the socket. SO_SNDBUF Sets the send buffer size. Takes an integer parameter and requires a system UIC or SYSPRV, BYPASS, or OPER privilege. Optional for a connectionless datagram. SO_SNDLOWAT Sets the low-water mark for a send() operation. Takes an integer parameter. SO_SNDTIMEO For Compaq use only. Sets the timeout value for a send() operation. SO_USELOOPBACK For Compaq use only. Valid for routing sockets. Determines if a sending socket receives a copy of its own message. Used when a set request on another socket type is ignored. Table 6-4 lists the TCP options available at the socket level.
Table 6-4 TCP Options TCP Option Description TCP_KEEPCNT When the SO_KEEPALIVE option is enabled, specifies the maximum number of keepalive probes to be sent. Default: 8. Takes an integer value, with a range of 1 to TCP_KEEPCNT. TCP_KEEPIDLE When the SO_KEEPALIVE option is enabled, specifies the number of seconds of idle time between keepalive probes. Default: 2 hours. Takes an integer value in the range of 1 to n, where n is TCP_KEEPIDLE divided by PR_SLOWHZ. TCP_KEEPINIT Specifies the number of seconds to wait before the connect attempt times out. Default: 75 seconds. For passive connections, the value is inherited from the listening socket. Takes an integer value in the range of 1 to n, where n is TCP_KEEPINIT divided by PR_SLOWHZ. TCP_KEEPINTVL When the SO_KEEPALIVE option is enabled, specifies the number of seconds to wait before retransmitting a keepalive probe. Default: 75 seconds. Takes an integer value in the range of 1 to n, where n is TCP_KEEPINTVL divided by PR_SLOWHZ. TCP_NODELAY Specifies that the send() operation will not be delayed to merge packets. TCP_MAXSEG Sets the maximum transmission unit (MTU) of a TCP segment to a specified integer value from 1 to 65,535. Default: 576 bytes. Can only be set before a listen() or connect() operation on the socket. For passive connections, the value is obtained from the listening socket. Note that TCP does not use an MTU value that is less than 32 or greater than the local network's MTU. Setting the option to zero results in the default behavior.
TCP_NODELACK When specified, disables the algorithm that gathers outstanding data that has not been acknowledged and sends it in a single packet when acknowledgement is received. Takes an integer value. Under most circumstances, TCP sends data when it is presented. When outstanding data has not yet been acknowledged, TCP gathers small amounts of the data into a single packet and sends it when an acknowledgement is received. This functionality can cause significant delays for some clients (such as windowing systems that send a stream of events from the mouse that do not expect replies).
Table 6-5 describes the IP options available at the socket level.
Table 6-5 IP Options IP Option Description IP_ADD_MEMBERSHIP Adds the host to the membership of a multicast group. A host must become a member of a multicast group before it can receive datagrams sent to the group. Membership is associated with a single interface; programs running on multihomed hosts may need to join the same group on more than one interface. Up to IP_MAX_MEMBERSHIPS (currently 20) memberships may be added on a single socket.
IP_DROP_MEMBERSHIP Removes the host from the membership of a multicast group. IP_HDRINCL If specified, the IP header is not prepended to the outgoing packet. IP_MULTICAST_IF For hosts with multiple interfaces. When specified, each multicast transmission is sent from the primary network interface. Overrides the default for subsequent transmissions from a given socket. IP_MULTICAST_LOOP Disables loopback of local delivery. If a multicast datagram is sent to a group of which the sending host is a member, a copy of the datagram is looped back by the IP layer for local delivery (default). To disable the loopback delivery, specify the value 0.
IP_MULTICAST_TTL Specifies the time-to-live (TTL) value for outgoing multicast datagrams. Takes an integer value between 0 and 255:
Value Action 0 Restricts distribution to applications running on the local host. 1 Forwards the multicast datagram to hosts on the local subnet. 1---255 With a multicast router attached to the sending host's network, forwards multicast datagrams beyond the local subnet. Multicast routers forward the datagram to known networks that have hosts belonging to the specified multicast group. The TTL value is decremented by each multicast router in the path. When the TTL value is decremented to 0, the datagram is no longer forwarded.
IP_OPTIONS Provides IP options to be transmitted in the IP header of each outgoing packet. IP_RECVDSTADDR Enables a SOCK_DGRAM socket to receive the destination IP address for a UDP datagram. IP_RECVOPTS Enables a SOCK_DGRAM socket to receive IP options. IP_TTL Time to live (TTL) for a datagram. IP_TOS Type of service (1-byte value). optval
Points to a buffer containing the parameters of the specified option.All socket level options other than SO_LINGER should be nonzero if the option is to be enabled, or zero if it is to be disabled.
SO_LINGER uses a linger structure parameter defined in the <socket.h> file. This structure specifies the desired state of the option and the linger interval. The option value for the SO_LINGER command is the address of a linger structure. See Section 5.8.4 for a description of the linger structure.
If the socket promises reliable delivery of data and l_onoff is nonzero, the system blocks the process on the close() attempt until it is able to transmit the data or until it decides it is unable to deliver the information. A timeout period, called the linger interval, is specified in l_linger.
If l_onoff is set to zero and a close() is issued, the system processes the close in a manner that allows the process to continue as quickly as possible.
optlen
An integer containing the size of the buffer pointed to by optval.
This routine manipulates options associated with a socket. Options can exist at multiple protocol levels. They are always present at the uppermost socket level.When manipulating socket options, specify the level at which the option resides and the name of the option. To manipulate options at the socket level, specify level as SOL_SOCKET. To manipulate options at any other level, supply the protocol number of the appropriate protocol controlling the option. For example, to indicate that an option is to be interpreted by TCP, set the level to the protocol number (IPPROTO_TCP) of TCP. See <in.h> for the various IPPROTO values.
0 Successful completion. --1 Error; errno is set to indicate the error.
[EBADF] The descriptor is invalid. [ENOTSOCK] The socket descriptor references a file, not a socket. [ENOPROTOOPT] The option is unknown. [EFAULT] The optname parameter is not a valid part of the user address space.
Returns the socket device channel (SDC) associated with a socket descriptor for direct use with DIGITAL TCP/IP Services for OpenVMS software.
Note
This routine only works with VAX C. Use the decc$get_sdc() routine with DEC C.
#include <socket.h>
short int vaxc$get_sdc (int s);
s
A socket descriptor.
This routine returns the SDC associated with a socket. C Socket descriptors are normally used either as file descriptors or with one of the routines that takes an explicit socket descriptor as its argument. C Sockets are implemented using TCP/IP socket device channels. This routine returns the SDC used by a given socket descriptor so you can use the TCP/IP facilities directly by means of various I/O system services ($QIO).
Note
The 64-bit return from OpenVMS Alpha systems has zero-extended bits in the high 32 bits of R0.
0 Indicates that s is not an open socket descriptor. x The SDC number.
This chapter contains a table of C Socket error codes and their OpenVMS system service equivalents. The C Socket routines use the DEC C compiler.
| C Socket (DEC C) Error Code |
Meaning | OpenVMS System Service Error Code |
|---|---|---|
| 0 | (success) | SS$_NORMAL |
| 1 EPERM | Not owner | SS$_ABORT |
| 2 ENOENT | No such file or directory | SS$_ABORT |
| 3 ESRCH | No such process | SS$_NOSUCHNODE |
| 4 EINTR | Interrupted system call | SS$_ABORT |
| 5 EIO | I/O error | SS$_ABORT |
| 6 ENXIO | No such device or address | SS$_NOSUCHDEV |
| 7 E2BIG | Argument list too long | SS$_ABORT |
| 8 ENOEXEC | Execution format error | SS$_ABORT |
| 9 EBADF | Bad file number | SS$_BADPARAM |
| 10 ECHILD | No children | SS$_ABORT |
| 11 EAGAIN | No more processes | SS$_ABORT |
| 12 ENOMEM | Not enough core | SS$_INSFMEM |
| 13 EACCES | Permission denied | SS$_ABORT |
| 14 EFAULT | Bad address | SS$_ACCVIO |
| 15 ENOTBLK | Block device required | SS$_ABORT |
| 16 EBUSY | Mount device busy | SS$_ABORT |
| 17 EEXIST | File exists | SS$_FILALRACC |
| 18 EXDEV | Cross-device link | SS$_ABORT |
| 19 ENODEV | No such device | SS$_ABORT |
| 20 ENOTDIR | Not a directory | SS$_ABORT |
| 21 EISDIR | Is a directory | SS$_ABORT |
| 22 EINVAL | Invalid argument | SS$_BADPARAM |
| 23 ENFILE | File table overflow | SS$_ABORT |
| 24 EMFILE | Too many open files | SS$_ABORT |
| 25 ENOTTY | Not a typewriter | SS$_ABORT |
| 26 ETXTBSY | Text file busy | SS$_ABORT |
| 27 EFBIG | File too large | SS$_ABORT |
| 28 ENOSPC | No space left on device | SS$_ABORT |
| 29 ESPIPE | Illegal seek | SS$_ABORT |
| 30 EROFS | Read-only file system | SS$_ABORT |
| 31 EMLINK | Too many links | SS$_ABORT |
| 32 EPIPE | Broken pipe | SS$_LINKDISCON |
| 33 EDOM | Argument too large | SS$_BADPARAM |
| 34 ERANGE | Result too large | SS$_TOOMUCHDATA |
| 35 EWOULDBLOCK | Operation would block | SS$_SUSPENDED |
| 36 EINPROGRESS | Operation now in progress | SS$_ABORT |
| 37 EALREADY | Operation already in progress | SS$_ABORT |
| 38 ENOTSOCK | Socket operation on non-socket | SS$_NOTNETDEV |
| 39 EDESTADDRREQ | Destination address required | SS$_NOSUCHNODE |
| 40 EMSGSIZE | Message too long | SS$_TOOMUCHDATA |
| 41 EPROTOTYPE | Protocol wrong type for socket | SS$_PROTOCOL |
| 42 ENOPROTOOPT | Protocol not available | SS$_PROTOCOL |
| 43 EPROTONOSUPPORT | Protocol not supported | SS$_PROTOCOL |
| 44 ESOCKTNOSUPPORT | Socket type not supported | SS$_PROTOCOL |
| 45 EOPNOTSUPP | Operation not supported on socket | SS$_ILLCNTRFUNC |
| 46 EPFNOSUPPORT | Protocol family not supported | SS$_PROTOCOL |
| 47 EAFNOSUPPORT | Address family not supported | SS$_PROTOCOL |
| 48 EADDRINUSE | Address already in use | SS$_DUPLNAM |
| 49 EADDRNOTAVAIL | Requested address cannot be assigned | SS$_IVADDR |
| 50 ENETDOWN | Network is down | SS$_UNREACHABLE |
| 51 ENETUNREACH | Network is unreachable | SS$_UNREACHABLE |
| 52 ENETRESET | Network dropped connection on reset | SS$_RESET |
| 53 ECONNABORTED | Software caused connection abort | SS$_LINKABORT |
| 54 ECONNRESET | Connection reset by peer | SS$_CONNECFAIL |
| 55 ENOBUFS | No buffer space available | SS$_INSFMEM |
| 56 EISCONN | Socket is already connected | SS$_FILALRACC |
| 57 ENOTCONN | Socket is not connected | SS$_NOLINKS |
| 58 ESHUTDOWN | Cannot send after socket shutdown | SS$_SHUT |
| 59 ETOOMANYREFS | Too many references, cannot splice | SS$_ABORT |
| 60 ETIMEDOUT | Connection timed out | SS$_TIMEOUT |
| 61 ECONNREFUSED | Connection refused | SS$_REJECT |
| 62 ELOOP | Too many levels of symbolic links | SS$_ABORT |
| 63 ENAMETOOLONG | File name too long | SS$_ABORT |
| 64 EHOSTDOWN | Host is down | SS$_SHUT |
| 65 EHOSTUNREACH | No route to host | SS$_UNREACHABLE |
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