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
20 The socket() function shall create an unbound socket in a communica‐
21 tions domain, and return a file descriptor that can be used in later
22 function calls that operate on sockets. The file descriptor shall be
23 allocated as described in Section 2.14, File Descriptor Allocation.
24 The socket() function takes the following arguments:
26 domain Specifies the communications domain in which a socket is to
28 be created.
29 type Specifies the type of socket to be created.
31 protocol Specifies a particular protocol to be used with the socket.
33 Specifying a protocol of 0 causes socket() to use an
34 unspecified default protocol appropriate for the requested
35 socket type.
36 The domain argument specifies the address family used in the communica‐
38 tions domain. The address families supported by the system are imple‐
39 mentation-defined.
40 Symbolic constants that can be used for the domain argument are defined
42 in the <sys/socket.h> header.
43 The type argument specifies the socket type, which determines the
45 semantics of communication over the socket. The following socket types
46 are defined; implementations may specify additional socket types:
47 SOCK_STREAM Provides sequenced, reliable, bidirectional, connection-
49 mode byte streams, and may provide a transmission mechanism
50 for out-of-band data.
51 SOCK_DGRAM Provides datagrams, which are connectionless-mode, unreli‐
53 able messages of fixed maximum length.
54 SOCK_SEQPACKET
56 Provides sequenced, reliable, bidirectional, connection-
57 mode transmission paths for records. A record can be sent
58 using one or more output operations and received using one
59 or more input operations, but a single operation never
60 transfers part of more than one record. Record boundaries
61 are visible to the receiver via the MSG_EOR flag.
62 If the protocol argument is non-zero, it shall specify a protocol that
64 is supported by the address family. If the protocol argument is zero,
65 the default protocol for this address family and type shall be used.
66 The protocols supported by the system are implementation-defined.
67 The process may need to have appropriate privileges to use the socket()
69 function or to create some sockets.
70
72 Upon successful completion, socket() shall return a non-negative inte‐
73 ger, the socket file descriptor. Otherwise, a value of -1 shall be
74 returned and errno set to indicate the error.
75
77 The socket() function shall fail if:
78 EAFNOSUPPORT
80 The implementation does not support the specified address fam‐
81 ily.
82 EMFILE All file descriptors available to the process are currently
84 open.
85 ENFILE No more file descriptors are available for the system.
87 EPROTONOSUPPORT
89 The protocol is not supported by the address family, or the pro‐
90 tocol is not supported by the implementation.
91 EPROTOTYPE
93 The socket type is not supported by the protocol.
94 The socket() function may fail if:
96 EACCES The process does not have appropriate privileges.
98 ENOBUFS
100 Insufficient resources were available in the system to perform
101 the operation.
102 ENOMEM Insufficient memory was available to fulfill the request.
104 The following sections are informative.
106
108 None.
109
111 The documentation for specific address families specifies which proto‐
112 cols each address family supports. The documentation for specific pro‐
113 tocols specifies which socket types each protocol supports.
114 The application can determine whether an address family is supported by
116 trying to create a socket with domain set to the protocol in question.
117
119 None.
120
122 None.
123
125 Section 2.14, File Descriptor Allocation, accept(), bind(), connect(),
126 getsockname(), getsockopt(), listen(), recv(), recvfrom(), recvmsg(),
127 send(), sendmsg(), setsockopt(), shutdown(), socketpair()
128 The Base Definitions volume of POSIX.1‐2017, <netinet_in.h>,
130 <sys_socket.h>
131
133 Portions of this text are reprinted and reproduced in electronic form
134 from IEEE Std 1003.1-2017, Standard for Information Technology -- Por‐
135 table Operating System Interface (POSIX), The Open Group Base Specifi‐
136 cations Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of
137 Electrical and Electronics Engineers, Inc and The Open Group. In the
138 event of any discrepancy between this version and the original IEEE and
139 The Open Group Standard, the original IEEE and The Open Group Standard
140 is the referee document. The original Standard can be obtained online
141 at http://www.opengroup.org/unix/online.html .
142 Any typographical or formatting errors that appear in this page are
144 most likely to have been introduced during the conversion of the source
145 files to man page format. To report such errors, see https://www.ker‐
146 nel.org/doc/man-pages/reporting_bugs.html .
147IEEE/The Open Group 2017 SOCKET(3P)