1CONNECT(P) POSIX Programmer's Manual CONNECT(P)
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6 connect - connect a socket
7
9 #include <sys/socket.h>
10 int connect(int socket, const struct sockaddr *address,
12 socklen_t address_len);
13
16 The connect() function shall attempt to make a connection on a socket.
17 The function takes the following arguments:
18 socket Specifies the file descriptor associated with the socket.
20 address
22 Points to a sockaddr structure containing the peer address. The
23 length and format of the address depend on the address family of
24 the socket.
25 address_len
27 Specifies the length of the sockaddr structure pointed to by the
28 address argument.
29 If the socket has not already been bound to a local address, connect()
32 shall bind it to an address which, unless the socket's address family
33 is AF_UNIX, is an unused local address.
34 If the initiating socket is not connection-mode, then connect() shall
36 set the socket's peer address, and no connection is made. For
37 SOCK_DGRAM sockets, the peer address identifies where all datagrams are
38 sent on subsequent send() functions, and limits the remote sender for
39 subsequent recv() functions. If address is a null address for the pro‐
40 tocol, the socket's peer address shall be reset.
41 If the initiating socket is connection-mode, then connect() shall
43 attempt to establish a connection to the address specified by the
44 address argument. If the connection cannot be established immediately
45 and O_NONBLOCK is not set for the file descriptor for the socket, con‐
46 nect() shall block for up to an unspecified timeout interval until the
47 connection is established. If the timeout interval expires before the
48 connection is established, connect() shall fail and the connection
49 attempt shall be aborted. If connect() is interrupted by a signal that
50 is caught while blocked waiting to establish a connection, connect()
51 shall fail and set errno to [EINTR], but the connection request shall
52 not be aborted, and the connection shall be established asynchronously.
53 If the connection cannot be established immediately and O_NONBLOCK is
55 set for the file descriptor for the socket, connect() shall fail and
56 set errno to [EINPROGRESS], but the connection request shall not be
57 aborted, and the connection shall be established asynchronously. Subse‐
58 quent calls to connect() for the same socket, before the connection is
59 established, shall fail and set errno to [EALREADY].
60 When the connection has been established asynchronously, select() and
62 poll() shall indicate that the file descriptor for the socket is ready
63 for writing.
64 The socket in use may require the process to have appropriate privi‐
66 leges to use the connect() function.
67
69 Upon successful completion, connect() shall return 0; otherwise, -1
70 shall be returned and errno set to indicate the error.
71
73 The connect() function shall fail if:
74 EADDRNOTAVAIL
76 The specified address is not available from the local machine.
77 EAFNOSUPPORT
79 The specified address is not a valid address for the address
80 family of the specified socket.
81 EALREADY
83 A connection request is already in progress for the specified
84 socket.
85 EBADF The socket argument is not a valid file descriptor.
87 ECONNREFUSED
89 The target address was not listening for connections or refused
90 the connection request.
91 EINPROGRESS
93 O_NONBLOCK is set for the file descriptor for the socket and the
94 connection cannot be immediately established; the connection
95 shall be established asynchronously.
96 EINTR The attempt to establish a connection was interrupted by deliv‐
98 ery of a signal that was caught; the connection shall be estab‐
99 lished asynchronously.
100 EISCONN
102 The specified socket is connection-mode and is already con‐
103 nected.
104 ENETUNREACH
106 No route to the network is present.
107 ENOTSOCK
109 The socket argument does not refer to a socket.
110 EPROTOTYPE
112 The specified address has a different type than the socket bound
113 to the specified peer address.
114 ETIMEDOUT
116 The attempt to connect timed out before a connection was made.
117 If the address family of the socket is AF_UNIX, then connect() shall
120 fail if:
121 EIO An I/O error occurred while reading from or writing to the file
123 system.
124 ELOOP A loop exists in symbolic links encountered during resolution of
126 the pathname in address.
127 ENAMETOOLONG
129 A component of a pathname exceeded {NAME_MAX} characters, or an
130 entire pathname exceeded {PATH_MAX} characters.
131 ENOENT A component of the pathname does not name an existing file or
133 the pathname is an empty string.
134 ENOTDIR
136 A component of the path prefix of the pathname in address is not
137 a directory.
138 The connect() function may fail if:
141 EACCES Search permission is denied for a component of the path prefix;
143 or write access to the named socket is denied.
144 EADDRINUSE
146 Attempt to establish a connection that uses addresses that are
147 already in use.
148 ECONNRESET
150 Remote host reset the connection request.
151 EHOSTUNREACH
153 The destination host cannot be reached (probably because the
154 host is down or a remote router cannot reach it).
155 EINVAL The address_len argument is not a valid length for the address
157 family; or invalid address family in the sockaddr structure.
158 ELOOP More than {SYMLOOP_MAX} symbolic links were encountered during
160 resolution of the pathname in address.
161 ENAMETOOLONG
163 Pathname resolution of a symbolic link produced an intermediate
164 result whose length exceeds {PATH_MAX}.
165 ENETDOWN
167 The local network interface used to reach the destination is
168 down.
169 ENOBUFS
171 No buffer space is available.
172 EOPNOTSUPP
174 The socket is listening and cannot be connected.
175 The following sections are informative.
178
180 None.
181
183 If connect() fails, the state of the socket is unspecified. Conforming
184 applications should close the file descriptor and create a new socket
185 before attempting to reconnect.
186
188 None.
189
191 None.
192
194 accept() , bind() , close() , getsockname() , poll() , select() ,
195 send() , shutdown() , socket() , the Base Definitions volume of
196 IEEE Std 1003.1-2001, <sys/socket.h>
197
199 Portions of this text are reprinted and reproduced in electronic form
200 from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
201 -- Portable Operating System Interface (POSIX), The Open Group Base
202 Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
203 Electrical and Electronics Engineers, Inc and The Open Group. In the
204 event of any discrepancy between this version and the original IEEE and
205 The Open Group Standard, the original IEEE and The Open Group Standard
206 is the referee document. The original Standard can be obtained online
207 at http://www.opengroup.org/unix/online.html .
208IEEE/The Open Group 2003 CONNECT(P)