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63 .\" Modified 1997-01-31 by Eric S. Raymond <esr@thyrsus.com>
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65 .\" Modified 2004-06-23 by Michael Kerrisk <mtk.manpages@gmail.com>
67 .TH CONNECT 2 2008-12-03 "Linux" "Linux Programmer's Manual"
69 connect \- initiate a connection on a socket
72 .BR "#include <sys/types.h>" " /* See NOTES */"
74 .B #include <sys/socket.h>
76 .BI "int connect(int " sockfd ", const struct sockaddr *" addr ,
77 .BI " socklen_t " addrlen );
82 system call connects the socket referred to by the file descriptor
84 to the address specified by
88 argument specifies the size of
90 The format of the address in
92 is determined by the address space of the socket
104 is the address to which datagrams are sent by default, and the only
105 address from which datagrams are received.
106 If the socket is of type
110 this call attempts to make a connection to the socket that is bound
111 to the address specified by
114 Generally, connection-based protocol sockets may successfully
116 only once; connectionless protocol sockets may use
118 multiple times to change their association.
119 Connectionless sockets may
120 dissolve the association by connecting to an address with the
126 (supported on Linux since kernel 2.2).
128 If the connection or binding succeeds, zero is returned.
129 On error, \-1 is returned, and
131 is set appropriately.
133 The following are general socket errors only.
134 There may be other domain-specific error codes.
137 For UNIX domain sockets, which are identified by pathname:
138 Write permission is denied on the socket file,
139 or search permission is denied for one of the directories
142 .BR path_resolution (7).)
144 .BR EACCES ", " EPERM
145 The user tried to connect to a broadcast address without having the socket
146 broadcast flag enabled or the connection request failed because of a local
150 Local address is already in use.
153 The passed address didn't have the correct address family in its
158 No more free local ports or insufficient entries in the routing cache.
161 see the description of
162 .I /proc/sys/net/ipv4/ip_local_port_range
164 for information on how to increase the number of local ports.
167 The socket is nonblocking and a previous connection attempt has not yet
171 The file descriptor is not a valid index in the descriptor table.
174 No-one listening on the remote address.
177 The socket structure address is outside the user's address space.
180 The socket is nonblocking and the connection cannot be completed
186 for completion by selecting the socket for writing.
189 indicates writability, use
197 completed successfully
199 is zero) or unsuccessfully
201 is one of the usual error codes listed here,
202 explaining the reason for the failure).
205 The system call was interrupted by a signal that was caught; see
207 .\" For TCP, the connection will complete asynchronously.
208 .\" See http://lkml.org/lkml/2005/7/12/254
211 The socket is already connected.
214 Network is unreachable.
217 The file descriptor is not associated with a socket.
220 Timeout while attempting connection.
221 The server may be too
222 busy to accept new connections.
223 Note that for IP sockets the timeout may
224 be very long when syncookies are enabled on the server.
228 function first appeared in 4.2BSD), POSIX.1-2001.
229 .\" SVr4 documents the additional
230 .\" general error codes
231 .\" .BR EADDRNOTAVAIL ,
233 .\" .BR EAFNOSUPPORT ,
240 .\" documents many additional error conditions not described here.
242 POSIX.1-2001 does not require the inclusion of
244 and this header file is not required on Linux.
245 However, some historical (BSD) implementations required this header
246 file, and portable applications are probably wise to include it.
248 The third argument of
252 (and this is what 4.x BSD and libc4 and libc5 have).
253 Some POSIX confusion resulted in the present
259 An example of the use of
269 .BR path_resolution (7)
271 This page is part of release 3.64 of the Linux
274 A description of the project,
275 and information about reporting bugs,
277 \%http://www.kernel.org/doc/man\-pages/.