1SOCKET(3P) POSIX Programmer's Manual SOCKET(3P)
2
6 This manual page is part of the POSIX Programmer's Manual. The Linux
7 implementation of this interface may differ (consult the corresponding
8 Linux manual page for details of Linux behavior), or the interface may
9 not be implemented on Linux.
10
12 socket - create an endpoint for communication
13
15 #include <sys/socket.h>
16 int socket(int domain, int type, int protocol);
18
21 The socket() function shall create an unbound socket in a communica‐
22 tions domain, and return a file descriptor that can be used in later
23 function calls that operate on sockets.
24 The socket() function takes the following arguments:
26 domain Specifies the communications domain in which a socket is to be
28 created.
29 type Specifies the type of socket to be created.
31 protocol
33 Specifies a particular protocol to be used with the socket.
34 Specifying a protocol of 0 causes socket() to use an unspecified
35 default protocol appropriate for the requested socket type.
36 The domain argument specifies the address family used in the communica‐
39 tions domain. The address families supported by the system are imple‐
40 mentation-defined.
41 Symbolic constants that can be used for the domain argument are defined
43 in the <sys/socket.h> header.
44 The type argument specifies the socket type, which determines the
46 semantics of communication over the socket. The following socket types
47 are defined; implementations may specify additional socket types:
48 SOCK_STREAM
50 Provides sequenced, reliable, bidirectional, connection-mode
51 byte streams, and may provide a transmission mechanism for out-
52 of-band data.
53 SOCK_DGRAM
55 Provides datagrams, which are connectionless-mode, unreliable
56 messages of fixed maximum length.
57 SOCK_SEQPACKET
59 Provides sequenced, reliable, bidirectional, connection-mode
60 transmission paths for records. A record can be sent using one
61 or more output operations and received using one or more input
62 operations, but a single operation never transfers part of more
63 than one record. Record boundaries are visible to the receiver
64 via the MSG_EOR flag.
65 If the protocol argument is non-zero, it shall specify a protocol that
68 is supported by the address family. If the protocol argument is zero,
69 the default protocol for this address family and type shall be used.
70 The protocols supported by the system are implementation-defined.
71 The process may need to have appropriate privileges to use the socket()
73 function or to create some sockets.
74
76 Upon successful completion, socket() shall return a non-negative inte‐
77 ger, the socket file descriptor. Otherwise, a value of -1 shall be
78 returned and errno set to indicate the error.
79
81 The socket() function shall fail if:
82 EAFNOSUPPORT
84 The implementation does not support the specified address fam‐
86 ily.
87 EMFILE No more file descriptors are available for this process.
89 ENFILE No more file descriptors are available for the system.
91 EPROTONOSUPPORT
93 The protocol is not supported by the address family, or the pro‐
95 tocol is not supported by the implementation.
96 EPROTOTYPE
98 The socket type is not supported by the protocol.
99 The socket() function may fail if:
102 EACCES The process does not have appropriate privileges.
104 ENOBUFS
106 Insufficient resources were available in the system to perform
107 the operation.
108 ENOMEM Insufficient memory was available to fulfill the request.
110 The following sections are informative.
113
115 None.
116
118 The documentation for specific address families specifies which proto‐
119 cols each address family supports. The documentation for specific pro‐
120 tocols specifies which socket types each protocol supports.
121 The application can determine whether an address family is supported by
123 trying to create a socket with domain set to the protocol in question.
124
126 None.
127
129 None.
130
132 accept(), bind(), connect(), getsockname(), getsockopt(), listen(),
133 recv(), recvfrom(), recvmsg(), send(), sendmsg(), setsockopt(), shut‐
134 down(), socketpair(), the Base Definitions volume of
135 IEEE Std 1003.1-2001, <netinet/in.h>, <sys/socket.h>
136
138 Portions of this text are reprinted and reproduced in electronic form
139 from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
140 -- Portable Operating System Interface (POSIX), The Open Group Base
141 Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
142 Electrical and Electronics Engineers, Inc and The Open Group. In the
143 event of any discrepancy between this version and the original IEEE and
144 The Open Group Standard, the original IEEE and The Open Group Standard
145 is the referee document. The original Standard can be obtained online
146 at http://www.opengroup.org/unix/online.html .
147IEEE/The Open Group 2003 SOCKET(3P)