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This chapter describes the Sockets API functions that are listed in Table 4-1.
| Function | Description |
|---|---|
| accept() | Accepts a connection on a passive socket. |
| bind() | Binds a name to a socket. |
| close() | Closes a connection and deletes a socket descriptor. |
| connect() | Initiates a connection on a socket. |
| decc$get_sdc() | Returns the socket device's OpenVMS I/O channel associated with a socket descriptor (for use with Compaq C). |
| gethostbyaddr() | Searches the hosts database for a host record with a given IPv4 address. |
| gethostbyname() | Searches the hosts database for a host record with a given name or alias. |
| gethostname() | Returns the fully qualified name of the local host. |
| getnameinfo() | Gets a node name and service name for an address and port number. |
| getnetbyaddr() | Searches the network database for a network record with a given address. |
| getnetbyname() | Searches the network database for a network record with a given name or alias. |
| getpeername() | Returns the name of the connected peer. |
| getprotobyname() | Searches the protocols database until a matching protocol name is found or until end of file is encountered. |
| getprotobynumber() | Searches the protocols database until a matching protocol number is found or until end of file is encountered. |
| getprotoent() | Reads the next line in the protocols database. |
| getservbyname() | Gets information on the named service from the network services database. |
| getservbyport() | Gets information on the named port from the network services database. |
| getsockname() | Returns the name associated with a socket. |
| getsockopt() | Returns the options set on a socket. |
| htonl() | Converts longwords from host byte order to network byte order. |
| htons() | Converts short integers from host byte order to network byte order. |
| inet_addr() | Converts internet addresses in text form into numeric internet addresses. |
| inet_lnaof() | Returns the local network address portion of an internet address. |
| inet_makeaddr() | Given a network address and a local address on that network, returns an internet address. |
| inet_netof() | Returns the internet network address portion of an internet address. |
| inet_network() | Converts a null-terminated text string representing an internet address into a network address in local host format. |
| inet_ntoa() | Converts an internet address into an ASCII (null-terminated) string. |
| ioctl() | Controls devices. Used for setting sockets for nonblocking I/O. |
| listen() | Sets the maximum limit of outstanding connection requests for a TCP socket. |
| ntohl() | Converts longwords from network byte order into host byte order. |
| ntohs() | Converts short integers from network byte order into host byte order. |
| read() | Reads bytes from a file or socket and places them into a user-defined buffer. |
| recv() | Receives bytes from a connected socket and places them into a user-defined buffer. |
| recvfrom() | Receives bytes for a socket from any source. |
| recvmsg() | Receives bytes on a socket and places them into scattered buffers. |
| select() | Allows the polling or checking of a group of sockets for I/O activity. |
| send() | Sends bytes through a socket to a connected peer. |
| sendmsg() | Sends gathered bytes through a socket to any other socket. |
| sendto() | Sends bytes through a socket to any other socket. |
| setsockopt() | Sets options on a socket. |
| shutdown() | Shuts down all or part of a bidirectional connection on a socket. |
| socket() | Creates an endpoint for communication by returning a socket descriptor. |
| write() | Writes bytes from a buffer to a file or socket. |
This section describes functions that comprise the Sockets API and that are supported by TCP/IP Services.
Accepts a connection on a passive socket.The $QIO equivalent is the IO$_ACCESS function with the IO$M_ACCEPT function modifier.
#include <types.h>#include <socket.h>
int accept ( int s, struct sockaddr *addr, int *addrlen );
s
A socket descriptor returned by socket() , subsequently bound to an address with bind() , which is listening for connections after a listen() .addr
A result parameter filled in with the address of the connecting entity, as known to the Communications layer. The exact format of the structure to which the address parameter points is determined by the domain in which the communication is occurring. This version of Compaq C supports only the internet domain (AF_INET).addrlen
A value/result argument. It should initially contain the size of the structure pointed to by addr. On return it will contain the actual length, in bytes, of the sockaddr structure that has been filled in by the Communications layer. See Section 3.2.7 for a description of the sockaddr structure.
This function completes the first connection on the queue of pending connections, creates a new socket with the same properties as s, and allocates and returns a new descriptor for the socket. If no pending connections are present on the queue and the socket is not marked as nonblocking, accept() blocks the caller until a connection request is present. If the socket is marked nonblocking by using a setsockopt() call and no pending connections are present on the queue, accept() returns an error. You cannot use the accepted socket to accept subsequent connections. The original socket s remains open (listening) for other connection requests. This call is used with connection-based socket types ( SOCK_STREAM ).Related Functions
See also bind() , connect() , listen() , select() , and socket() .
x A nonnegative integer that is a descriptor for the accepted socket. -1 Error; errno is set to indicate the error.
EBADF The socket descriptor is invalid. ECONNABORTED A connection has been aborted. EFAULT The addr argument is not in a writable part of the user address space. EINTR The accept() function was interrupted by a signal before a valid connection arrived. EINVAL The socket is not accepting connections. EMFILE There are too many open file descriptors. ENFILE The maximum number of file descriptors in the system is already open. ENETDOWN TCP/IP Services was not started. ENOBUFS The system has insufficient resources to complete the call. ENOMEM The system was unable to allocate kernel memory. ENOTSOCK The socket descriptor is invalid. EOPNOTSUPP The reference socket is not of type SOCK_STREAM . EPROTO A protocol error occurred. EWOULDBLOCK The socket is marked nonblocking, and no connections are present to be accepted.
Binds a name to a socket.The $QIO equivalent is the IO$_SETMODE function with the p3 argument.
#include <types.h>#include <socket.h>
int bind ( int s, struct sockaddr *name, int namelen );
s
A socket descriptor created with the socket() function .name
Address of a structure used to assign a name to the socket in the format specific to the family (AF_INET) socket address. See Section 3.2.7 for a description of the sockaddr structure.namelen
The size, in bytes, of the structure pointed to by name.
This function assigns a port number and IP address to an unnamed socket. When a socket is created with the socket() function, it exists in a name space (address family) but has no name assigned. The bind() function requests that a name be assigned to the socket.Related Functions
See also connect() , getsockname() , listen() , and socket() .
0 Successful completion. -1 Error; errno is set to indicate the error.
EACCESS The requested address is protected, and the current user has inadequate permission to access it. EADDRINUSE The specified internet address and ports are already in use. EADDRNOTAVAIL The specified address is not available from the local machine. EAFNOSUPPORT The specified address is invalid for the address family of the specified socket. EBADF The socket descriptor is invalid. EDESTADDRREQ The address argument is a null pointer. EFAULT The name argument is not a valid part of the user address space. EINVAL The socket is already bound to an address and the protocol does not support binding to a new address, the socket has been shut down, or the length or the namelen argument is invalid for the address family. EISCONN The socket is already connected. EISDIR The address argument is a null pointer. ENOBUFS The system has insufficient resources to complete the call. ENOTSOCK The socket descriptor is invalid. EOPNOTSUPP The socket type of the specified socket does not support binding to an address.
Closes a connection and deletes a socket descriptor.The $QIO equivalent is the $DASSGN system service.
#include <unixio.h>int close ( s );
s
A socket descriptor.
This function deletes a descriptor from the per-process object (Compaq C structure) reference table. Associated TCP connections close first.If a call to the connect() function fails for a connection mode socket, applications should use close() to deallocate the socket and descriptor.
Related Functions
See also accept() , socket() , and write() .
0 Successful completion. -1 Error; errno is set to indicate the error.
EBADF The socket descriptor is invalid. EINTR The close() function was interrupted by a signal that was caught.
Initiates a connection on a socket.The $QIO equivalent is the IO$_ACCESS function.
#include <types.h>#include <socket.h>
int connect ( int s, struct sockaddr *name, int namelen );
s
A socket descriptor created with socket() .name
The address of a structure that specifies the name of the remote socket in the format specific to the address family (AF_INET).namelen
The size, in bytes, of the structure pointed to by name.
If s is a socket descriptor of type SOCK_DGRAM , then this call permanently specifies the peer where the data is sent. If s is of type SOCK_STREAM , then this call attempts to make a connection to the specified socket.Each communications space interprets the name argument. This argument specifies the socket that is connected to the socket specified in s.
If the connect() function fails for a connection-mode socket, applications should use the close() function to deallocate the socket and descriptor. If attempting to reinitiate the connection, applications should create a new socket.
Related Functions
See also accept() , select() , socket() , getsockname() , and shutdown() .
0 Successful completion. -1 Error; errno is set to indicate the error.
EADDRINUSE Configuration problem. There are insufficient ports available for the attempted connection. The ipport_userreserved variable of the inet subsystem should be increased. EADDRNOTAVAIL The specified address is not available from the local machine. EAFNOSUPPORT The addresses in the specified address family cannot be used with this socket. EALREADY A connection request is already in progress for the specified socket. EBADF The socket descriptor is invalid. ECONNREFUSED The attempt to connect was rejected. EFAULT The name argument is not a valid part of the user address space. EHOSTUNREACH The specified host is not reachable. EINPROGRESS O_NONBLOCK is set for the file descriptor for the socket, and the connection cannot be immediately established; the connection will be established asynchronously. EINTR The connect() function was interrupted by a signal while waiting for the connection to be established. Once established, the connection may continue asynchronously. EINVAL The value of the namelen argument is invalid for the specified address family, or the sa_family field in the socket address structure is invalid for the protocol. EISCONN The socket is already connected. ELOOP Too many symbolic links were encountered in translating the file specification in the address. ENETDOWN The local network connection is not operational. ENETUNREACH No route to the network or host is present. ENOBUFS The system has insufficient resources to complete the call. ENOTSOCK The socket descriptor is invalid. EOPNOTSUPP The socket is listening and cannot be connected. EPROTOTYPE The specified address has a different type than the socket bound to the specified peer address. ETIMEDOUT The connection request timed out without establishing a connection. EWOULDBLOCK The socket is nonblocking, and the connection cannot be completed immediately. It is possible to use the select() function to select the socket for writing.
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