socket(3p) — Linux manual page

SOCKET(3P)              POSIX Programmer's Manual             SOCKET(3P)

PROLOG

       This manual page is part of the POSIX Programmer's Manual.  The
       Linux implementation of this interface may differ (consult the
       corresponding Linux manual page for details of Linux behavior),
       or the interface may not be implemented on Linux.

NAME

       socket — create an endpoint for communication

SYNOPSIS

       #include <sys/socket.h>

       int socket(int domain, int type, int protocol);

DESCRIPTION

       The socket() function shall create an unbound socket in a
       communications domain, and return a file descriptor that can be
       used in later function calls that operate on sockets. The file
       descriptor shall be allocated as described in Section 2.14, File
       Descriptor Allocation.

       The socket() function takes the following arguments:

       domain      Specifies the communications domain in which a socket
                   is to be created.

       type        Specifies the type of socket to be created.

       protocol    Specifies a particular protocol to be used with the
                   socket. Specifying a protocol of 0 causes socket() to
                   use an unspecified default protocol appropriate for
                   the requested socket type.

       The domain argument specifies the address family used in the
       communications domain. The address families supported by the
       system are implementation-defined.

       Symbolic constants that can be used for the domain argument are
       defined in the <sys/socket.h> header.

       The type argument specifies the socket type, which determines the
       semantics of communication over the socket. The following socket
       types are defined; implementations may specify additional socket
       types:

       SOCK_STREAM Provides sequenced, reliable, bidirectional,
                   connection-mode byte streams, and may provide a
                   transmission mechanism for out-of-band data.

       SOCK_DGRAM  Provides datagrams, which are connectionless-mode,
                   unreliable messages of fixed maximum length.

       SOCK_SEQPACKET
                   Provides sequenced, reliable, bidirectional,
                   connection-mode transmission paths for records. A
                   record can be sent using one or more output
                   operations and received using one or more input
                   operations, but a single operation never transfers
                   part of more than one record. Record boundaries are
                   visible to the receiver via the MSG_EOR flag.

       If the protocol argument is non-zero, it shall specify a protocol
       that is supported by the address family. If the protocol argument
       is zero, the default protocol for this address family and type
       shall be used. The protocols supported by the system are
       implementation-defined.

       The process may need to have appropriate privileges to use the
       socket() function or to create some sockets.

RETURN VALUE

       Upon successful completion, socket() shall return a non-negative
       integer, the socket file descriptor.  Otherwise, a value of -1
       shall be returned and errno set to indicate the error.

ERRORS

       The socket() function shall fail if:

       EAFNOSUPPORT
              The implementation does not support the specified address
              family.

       EMFILE All file descriptors available to the process are
              currently open.

       ENFILE No more file descriptors are available for the system.

       EPROTONOSUPPORT
              The protocol is not supported by the address family, or
              the protocol is not supported by the implementation.

       EPROTOTYPE
              The socket type is not supported by the protocol.

       The socket() function may fail if:

       EACCES The process does not have appropriate privileges.

       ENOBUFS
              Insufficient resources were available in the system to
              perform the operation.

       ENOMEM Insufficient memory was available to fulfill the request.

       The following sections are informative.

EXAMPLES

       None.

APPLICATION USAGE

       The documentation for specific address families specifies which
       protocols each address family supports. The documentation for
       specific protocols specifies which socket types each protocol
       supports.

       The application can determine whether an address family is
       supported by trying to create a socket with domain set to the
       protocol in question.

RATIONALE

       None.

FUTURE DIRECTIONS

       None.

SEE ALSO

       Section 2.14, File Descriptor Allocation, accept(3p), bind(3p),
       connect(3p), getsockname(3p), getsockopt(3p), listen(3p),
       recv(3p), recvfrom(3p), recvmsg(3p), send(3p), sendmsg(3p),
       setsockopt(3p), shutdown(3p), socketpair(3p)

       The Base Definitions volume of POSIX.1‐2017, netinet_in.h(0p),
       sys_socket.h(0p)

COPYRIGHT

       Portions of this text are reprinted and reproduced in electronic
       form from IEEE Std 1003.1-2017, Standard for Information
       Technology -- Portable Operating System Interface (POSIX), The
       Open Group Base Specifications Issue 7, 2018 Edition, Copyright
       (C) 2018 by the Institute of Electrical and Electronics
       Engineers, Inc and The Open Group.  In the event of any
       discrepancy between this version and the original IEEE and The
       Open Group Standard, the original IEEE and The Open Group
       Standard is the referee document. The original Standard can be
       obtained online at http://www.opengroup.org/unix/online.html .

       Any typographical or formatting errors that appear in this page
       are most likely to have been introduced during the conversion of
       the source files to man page format. To report such errors, see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .

IEEE/The Open Group               2017                        SOCKET(3P)

Pages that refer to this page: sys_socket.h(0p), sys_un.h(0p), accept(3p), bind(3p), connect(3p), fdopen(3p), freeaddrinfo(3p), getnameinfo(3p), getpeername(3p), getsockname(3p), getsockopt(3p), listen(3p), recv(3p), recvfrom(3p), recvmsg(3p), send(3p), sendmsg(3p), sendto(3p), setsockopt(3p), shutdown(3p), socketpair(3p)

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