1socket(3SOCKET) Sockets Library Functions socket(3SOCKET)
2
6 socket - create an endpoint for communication
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9 cc [ flag ... ] file ... -lsocket -lnsl [ library ... ]
10 #include <sys/types.h>
11 #include <sys/socket.h>
12 int socket(int domain, int type, int protocol);
14
17 The socket() function creates an endpoint for communication and returns
18 a descriptor.
19 The domain argument specifies the protocol family within which communi‐
22 cation takes place. The protocol family is generally the same as the
23 address family for the addresses supplied in later operations on the
24 socket. These families are defined in <sys/socket.h>.
25 The currently supported protocol families are:
28 PF_UNIX UNIX system internal protocols
30 PF_INET Internet Protocol Version 4 (IPv4)
33 PF_INET6 Internet Protocol Version 6 (IPv6)
36 PF_NCA Network Cache and Accelerator (NCA) protocols
39 The socket has the indicated type, which specifies the communication
43 semantics. Currently defined types are:
44 SOCK_STREAM
46 SOCK_DGRAM
47 SOCK_RAW
48 SOCK_SEQPACKET
49 SOCK_RDM
50 There must be an entry in the netconfig(4) file for at least each pro‐
54 tocol family and type required. If a non-zero protocol has been speci‐
55 fied but no exact match for the protocol family, type, and protocol is
56 found, then the first entry containing the specified family and type
57 with a protocol value of zero will be used.
58 A SOCK_STREAM type provides sequenced, reliable, two-way connection-
61 based byte streams. An out-of-band data transmission mechanism may be
62 supported. A SOCK_DGRAM socket supports datagrams (connectionless,
63 unreliable messages of a fixed (typically small) maximum length). A
64 SOCK_SEQPACKET socket may provide a sequenced, reliable, two-way con‐
65 nection-based data transmission path for datagrams of fixed maximum
66 length; a consumer may be required to read an entire packet with each
67 read system call. This facility is protocol specific, and presently not
68 implemented for any protocol family. SOCK_RAW sockets provide access to
69 internal network interfaces. The types SOCK_RAW, which is available
70 only to a user with the net_rawaccess privilege, and SOCK_RDM, for
71 which no implementation currently exists, are not described here.
72 The protocol parameter is a protocol-family-specific value which speci‐
75 fies a particular protocol to be used with the socket. Normally this
76 value is zero, as commonly only a single protocol exists to support a
77 particular socket type within a given protocol family. However, multi‐
78 ple protocols may exist, in which case a particular protocol may be
79 specified in this manner.
80 Sockets of type SOCK_STREAM are full-duplex byte streams, similar to
83 pipes. A stream socket must be in a connected state before any data may
84 be sent or received on it. A connection to another socket is created
85 with a connect(3SOCKET) call. Once connected, data may be transferred
86 using read(2) and write(2) calls or some variant of the send(3SOCKET)
87 and recv(3SOCKET) calls. When a session has been completed, a close(2)
88 may be performed. Out-of-band data may also be transmitted as described
89 on the send(3SOCKET) manual page and received as described on the
90 recv(3SOCKET) manual page.
91 The communications protocols used to implement a SOCK_STREAM insure
94 that data is not lost or duplicated. If a piece of data for which the
95 peer protocol has buffer space cannot be successfully transmitted
96 within a reasonable length of time, then the connection is considered
97 broken and calls will indicate an error with −1 returns and with
98 ETIMEDOUT as the specific code in the global variable errno. The proto‐
99 cols optionally keep sockets "warm" by forcing transmissions roughly
100 every minute in the absence of other activity. An error is then indi‐
101 cated if no response can be elicited on an otherwise idle connection
102 for a extended period (for instance 5 minutes). A SIGPIPE signal is
103 raised if a thread sends on a broken stream; this causes naive pro‐
104 cesses, which do not handle the signal, to exit.
105 SOCK_SEQPACKET sockets employ the same system calls as SOCK_STREAM
108 sockets. The only difference is that read(2) calls will return only
109 the amount of data requested, and any remaining in the arriving packet
110 will be discarded.
111 SOCK_DGRAM and SOCK_RAW sockets allow datagrams to be sent to corre‐
114 spondents named in sendto(3SOCKET) calls. Datagrams are generally
115 received with recvfrom(3SOCKET), which returns the next datagram with
116 its return address.
117 An fcntl(2) call can be used to specify a process group to receive a
120 SIGURG signal when the out-of-band data arrives. It can also enable
121 non-blocking I/O.
122 The operation of sockets is controlled by socket level options. These
125 options are defined in the file <sys/socket.h>. setsockopt(3SOCKET) and
126 getsockopt(3SOCKET) are used to set and get options, respectively.
127
129 Upon successful completion, a descriptor referencing the socket is
130 returned. Otherwise, -1 is returned and errno is set to indicate the
131 error.
132
134 The socket() function will fail if:
135 EACCES Permission to create a socket of the specified type
137 or protocol is denied.
138 EAGAIN There were insufficient resources available to com‐
141 plete the operation.
142 EAFNOSUPPORT The specified address family is not supported by the
145 protocol family.
146 EMFILE The per-process descriptor table is full.
149 ENOMEM Insufficient user memory is available.
152 ENOSR There were insufficient STREAMS resources available
155 to complete the operation.
156 EPFNOSUPPORT The specified protocol family is not supported.
159 EPROTONOSUPPORT The protocol type is not supported by the address
162 family.
163 EPROTOTYPE The socket type is not supported by the protocol.
166
169 See attributes(5) for descriptions of the following attributes:
170 ┌─────────────────────────────┬─────────────────────────────┐
175 │ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
176 ├─────────────────────────────┼─────────────────────────────┤
177 │MT-Level │Safe │
178 └─────────────────────────────┴─────────────────────────────┘
179
181 nca(1), close(2), fcntl(2), ioctl(2), read(2), write(2),
182 accept(3SOCKET), bind(3SOCKET), connect(3SOCKET), getsockname(3SOCKET),
183 getsockopt(3SOCKET), in.h(3HEAD),listen(3SOCKET), recv(3SOCKET), set‐
184 sockopt(3SOCKET), send(3SOCKET), shutdown(3SOCKET), socket.h(3HEAD),
185 socketpair(3SOCKET), attributes(5)
186
188 Historically, AF_* was commonly used in places where PF_* was meant.
189 New code should be careful to use PF_* as necessary.
190SunOS 5.11 28 Jan 2009 socket(3SOCKET)