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.\" Copyright 1993 Rickard E. Faith (faith@cs.unc.edu)
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.\" Modified Fri Jan 31 16:22:26 1997 by Eric S. Raymond <esr@thyrsus.com>
.\"
.TH CONNECT 2 "23 July 1993" "Linux 0.99.11" "Linux Programmer's Manual"
.SH NAME
connect \- initiate a connection on a socket
.SH SYNOPSIS
.B #include <sys/types.h>
.br
.B #include <sys/socket.h>
.sp
.BI "int connect(int " sockfd ", struct sockaddr *" serv_addr ", socklen_t
.BI " addrlen );
.SH DESCRIPTION
The parameter
.I sockfd
is a socket.
If it is of type
.BR SOCK_DGRAM ,
this call specifies the peer with which the socket is to be associated;
this address is that to which datagrams are to be sent, and the only
address from which datagrams are to be received.  If the socket is of type
.B SOCK_STREAM ,
this call attempts to make a connection to another socket.  The other
socket is specified by
.BR serv_addr ,
which is an address in the communications space of the socket.  Each
communications space interprets the
.BR serv_addr ,
parameter in its own way.  Generally, stream sockets may successfully
.B connect
only once; datagram sockets may use
.B connect
multiple times to change their association.  Datagram sockets may dissolve
the association by connecting to an invalid address, such as a null
address.
.SH "RETURN VALUE"
If the connection or binding succeeds, zero is returned.  On error, \-1 is
returned, and
.I errno
is set appropriately.
.SH ERRORS
The following are general socket errors only.  There may be other
domain-specific error codes. 
.TP 0.8i
.B EBADF
Bad descriptor.
.TP
.B EFAULT
The socket structure address is outside your address space.
.TP
.B ENOTSOCK
The descriptor is not associated with a socket.
.TP
.B EISCONN
The socket is already connected.
.TP
.B ECONNREFUSED
Connection refused at server.
.TP
.B ETIMEDOUT
Timeout while attempting connection.
.TP
.B ENETUNREACH
Network is unreachable.
.TP
.B EADDRINUSE
Address is already in use.
.TP
.B EINPROGRESS
The socket is non-blocking and the connection cannot be completed
immediately.  It is possible to
.BR select (2)
for completion by selecting the socket for writing. After \fBselect\fR
indicates writability, use
.BR getsockopt (2)
to read the \fBSO_ERROR\fR option at level \fBSOL_SOCKET\fR to determine
whether \fBconnect\fR completed successfully (\fBSO_ERROR\fR is zero) or
unsuccessfully (\fBSO_ERROR\fR is one of the usual error codes listed
above, explaining the reason for the failure).
.TP
.B EALREADY
The socket is non-blocking and a previous connection attempt has not yet
been completed.
.SH CONFORMING TO
SVr4, 4.4BSD (the
.B connect
function first appeared in BSD 4.2).  SVr4 documents additional
general error codes EADDRNOTAVAIL, EINVAL, EAFNOSUPPORT, 
EALREADY, EINTR, EPROTOTYPE, ENOSR.  It also
documents many additional error conditions not described here.
.SH "SEE ALSO"
.BR accept "(2), " bind "(2), " listen "(2), "
.BR socket "(2), " getsockname (2)