.\" Copyright (c) 2008 Renzo Davoli .\" .\" This is free documentation; you can redistribute it and/or .\" modify it under the terms of the GNU General Public License, .\" version 2, as published by the Free Software Foundation. .\" .\" The GNU General Public License's references to "object code" .\" and "executables" are to be interpreted as the output of any .\" document formatting or typesetting system, including .\" intermediate and printed output. .\" .\" This manual is distributed in the hope that it will be useful, .\" but WITHOUT ANY WARRANTY; without even the implied warranty of .\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the .\" GNU General Public License for more details. .\" .\" You should have received a copy of the GNU General Public .\" License along with this manual; if not, write to the Free .\" Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, .\" MA 02110-1301 USA. .\" .\" .\" Modified from socket(2) manual page: its license follows. .\" Copyright (c) 1983, 1991 The Regents of the University of California. .\" All rights reserved. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. All advertising materials mentioning features or use of this software .\" must display the following acknowledgement: .\" This product includes software developed by the University of .\" California, Berkeley and its contributors. .\" 4. Neither the name of the University nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE .\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF .\" SUCH DAMAGE. .\" .\" $Id: socket.2,v 1.4 1999/05/13 11:33:42 freitag Exp $ .\" .\" Modified 1993-07-24 by Rik Faith .\" Modified 1996-10-22 by Eric S. Raymond .\" Modified 1998, 1999 by Andi Kleen .\" Modified 2002-07-17 by Michael Kerrisk .\" Modified 2004-06-17 by Michael Kerrisk .\" Modified 2008-04-23 by Renzo Davoli .\" .TH MSOCKET 2VIEWOS 2008-04-23 "View-OS" "Linux/View-OS Programmer's Manual" .SH NAME msocket \- create an endpoint for communication in a multi-stack environment .SH SYNOPSIS .BR "#include " " /* See NOTES */" .br .B #include .sp .BI "int msocket(char * " path ", int " domain ", int " type ", int " protocol ); .SH DESCRIPTION .BR msocket () creates an endpoint for communication and returns a descriptor in a multi-stack environment or defines the default stack. .PP The .I path parameter selects the stack used for the call. The path must refer to a stack special file (S_IFSTACK). When path is NULL, the default stack gets used. It is possible to specify a default network stack for each domain (see SOCK_DEFAULT below). .PP The .I domain parameter specifies a communication domain; this selects the protocol family which will be used for communication. These families are defined in .IR . The currently understood formats include: .TS tab(:); l l l. Name:Purpose:Man page T{ .BR PF_UNIX ", " PF_LOCAL T}:T{ Local communication T}:T{ .BR unix (7) T} T{ .B PF_INET T}:IPv4 Internet protocols:T{ .BR ip (7) T} T{ .B PF_INET6 T}:IPv6 Internet protocols:T{ .BR ipv6 (7) T} T{ .B PF_IPX T}:IPX \- Novell protocols: T{ .B PF_NETLINK T}:T{ Kernel user interface device T}:T{ .BR netlink (7) T} T{ .B PF_X25 T}:ITU-T X.25 / ISO-8208 protocol:T{ .BR x25 (7) T} T{ .B PF_AX25 T}:T{ Amateur radio AX.25 protocol T}: T{ .B PF_ATMPVC T}:Access to raw ATM PVCs: T{ .B PF_APPLETALK T}:Appletalk:T{ .BR ddp (7) T} T{ .B PF_PACKET T}:T{ Low level packet interface T}:T{ .BR packet (7) T} .TE .PP The socket has the indicated .IR type , which specifies the communication semantics or .B SOCK_DEFAULT to define the standard stack for the specified domain(s). Currently defined types are: .TP .B SOCK_STREAM Provides sequenced, reliable, two-way, connection-based byte streams. An out-of-band data transmission mechanism may be supported. .TP .B SOCK_DGRAM Supports datagrams (connectionless, unreliable messages of a fixed maximum length). .TP .B SOCK_SEQPACKET Provides a sequenced, reliable, two-way connection-based data transmission path for datagrams of fixed maximum length; a consumer is required to read an entire packet with each input system call. .TP .B SOCK_RAW Provides raw network protocol access. .TP .B SOCK_RDM Provides a reliable datagram layer that does not guarantee ordering. .TP .B SOCK_PACKET Obsolete and should not be used in new programs; see .BR packet (7). .PP Some socket types may not be implemented by all protocol families; for example, .B SOCK_SEQPACKET is not implemented for .BR AF_INET . .PP When .IR type is .B SOCK_DEFAULT msocket does not define any communication endpoint, instead it defines the stack that will be used for the following msocket calls with NULL path, or for the following obsolete .BR socket (2) calls. Default stacks get inherited through process creation .BR fork (2) and execution .BR execve (2). When .IR type is .B SOCK_DEFAULT and .IR domain is .B PF_UNSPEC the named stack becames the default stack for all the protocols it supports. .PP The .I protocol specifies a particular protocol to be used with the socket. Normally only a single protocol exists to support a particular socket type within a given protocol family, in which case .I protocol can be specified as 0. However, it is possible that many protocols may exist, in which case a particular protocol must be specified in this manner. The protocol number to use is specific to the \*(lqcommunication domain\*(rq in which communication is to take place; see .BR protocols (5). See .BR getprotoent (3) on how to map protocol name strings to protocol numbers. .PP Sockets of type .B SOCK_STREAM are full-duplex byte streams, similar to pipes. They do not preserve record boundaries. A stream socket must be in a .I connected state before any data may be sent or received on it. A connection to another socket is created with a .BR connect (2) call. Once connected, data may be transferred using .BR read (2) and .BR write (2) calls or some variant of the .BR send (2) and .BR recv (2) calls. When a session has been completed a .BR close (2) may be performed. Out-of-band data may also be transmitted as described in .BR send (2) and received as described in .BR recv (2). .PP The communications protocols which implement a .B SOCK_STREAM ensure that data is not lost or duplicated. If a piece of data for which the peer protocol has buffer space cannot be successfully transmitted within a reasonable length of time, then the connection is considered to be dead. When .B SO_KEEPALIVE is enabled on the socket the protocol checks in a protocol-specific manner if the other end is still alive. A .B SIGPIPE signal is raised if a process sends or receives on a broken stream; this causes naive processes, which do not handle the signal, to exit. .B SOCK_SEQPACKET sockets employ the same system calls as .B SOCK_STREAM sockets. The only difference is that .BR read (2) calls will return only the amount of data requested, and any data remaining in the arriving packet will be discarded. Also all message boundaries in incoming datagrams are preserved. .PP .B SOCK_DGRAM and .B SOCK_RAW sockets allow sending of datagrams to correspondents named in .BR sendto (2) calls. Datagrams are generally received with .BR recvfrom (2), which returns the next datagram along with the address of its sender. .PP .B SOCK_PACKET is an obsolete socket type to receive raw packets directly from the device driver. Use .BR packet (7) instead. .PP An .BR fcntl (2) .B F_SETOWN operation can be used to specify a process or process group to receive a .B SIGURG signal when the out-of-band data arrives or .B SIGPIPE signal when a .B SOCK_STREAM connection breaks unexpectedly. This operation may also be used to set the process or process group that receives the I/O and asynchronous notification of I/O events via .BR SIGIO . Using .B F_SETOWN is equivalent to an .BR ioctl (2) call with the .B FIOSETOWN or .B SIOCSPGRP argument. .PP When the network signals an error condition to the protocol module (e.g., using a ICMP message for IP) the pending error flag is set for the socket. The next operation on this socket will return the error code of the pending error. For some protocols it is possible to enable a per-socket error queue to retrieve detailed information about the error; see .B IP_RECVERR in .BR ip (7). .PP The operation of sockets is controlled by socket level .IR options . These options are defined in .IR . The functions .BR setsockopt (2) and .BR getsockopt (2) are used to set and get options, respectively. .SH "RETURN VALUE" On success, a file descriptor for the new socket is returned except when .IR type is .BR SOCK_DEFAULT. In this latter case 0 is returned on success. On error, \-1 is returned, and .I errno is set appropriately. .SH ERRORS .TP .B EACCES Permission to create a socket of the specified type and/or protocol is denied. .TP .B EAFNOSUPPORT The implementation does not support the specified address family. .TP .B EINVAL Unknown protocol, or protocol family not available. .TP .B EMFILE Process file table overflow. .TP .B ENFILE The system limit on the total number of open files has been reached. .TP .BR ENOBUFS " or " ENOMEM Insufficient memory is available. The socket cannot be created until sufficient resources are freed. .TP .B EPROTONOSUPPORT The protocol type or the specified protocol is not supported within this domain. .PP Other errors may be generated by the underlying protocol modules. .SH "CONFORMING TO" This is a system call defined for View-OS. It extends .BR socket (), appeared in 4.2BSD and conforming to 4.4BSD, POSIX.1-2001. System providing .BR msocket () do provide also a .BR socket () call for backward compatibility. In fact: .BR "socket(domain,type,protocol)" is equivalent to .BR "msocket(NULL,domain,type,protocol)" In this way it is generally portable to/from non-BSD systems supporting clones of the BSD socket layer (including System V variants). .SH NOTES POSIX.1-2001 does not require the inclusion of .IR , and this header file is not required on Linux. However, some historical (BSD) implementations required this header file, and portable applications are probably wise to include it. The manifest constants used under 4.x BSD for protocol families are .BR PF_UNIX , .BR PF_INET , etc., while .B AF_UNIX etc. are used for address families. However, already the BSD man page promises: "The protocol family generally is the same as the address family", and subsequent standards use AF_* everywhere. The header file .I is only required for libc4 or earlier. Some packages, like util-linux, claim portability to all Linux versions and libraries. They certainly need this header file. .SH BUGS .B SOCK_UUCP is not implemented yet. .\"SH EXAMPLE .\"An example of the use of .\"BR socket () .\"s shown in .\"BR getaddrinfo (3). .SH "SEE ALSO" .BR socket (2), .BR accept (2), .BR bind (2), .BR connect (2), .BR fcntl (2), .BR getpeername (2), .BR getsockname (2), .BR getsockopt (2), .BR ioctl (2), .BR listen (2), .BR read (2), .BR recv (2), .BR select (2), .BR send (2), .BR shutdown (2), .BR socketpair (2), .BR write (2), .BR getprotoent (3), .BR ip (7), .BR socket (7), .BR tcp (7), .BR udp (7), .BR unix (7) .PP .SH COLOPHON This page has been modified from .BR socket (2) page of release 2.79 of the Linux. In fact .BR msocket (2) is an extension of this call. .I man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/. .PP View-OS is a project of the Computer Science Department, University of Bologna. Project Leader: Renzo Davoli. .br Howto's and further information can be found on the project wiki .br .