CONNECT(2)						     Linux Programmer's Manual							CONNECT(2)

NAME

       connect - initiate a connection on a socket

SYNOPSIS

       #include <sys/types.h>
       #include <sys/socket.h>

       int connect(int sockfd, const struct sockaddr *serv_addr, socklen_t addrlen);

DESCRIPTION

       The  file descriptor sockfd must refer to a socket.  If the socket is of type SOCK_DGRAM then the serv_addr address is the address to which
       datagrams are sent by default, and the only address from which datagrams are received.  If the socket is of type SOCK_STREAM  or  SOCK_SEQ-
       PACKET,	this  call  attempts  to make a connection to another socket.  The other socket is specified by serv_addr, which is an address (of
       length addrlen) in the communications space of the socket.  Each communications space interprets the serv_addr parameter in its own way.

       Generally, connection-based protocol sockets may successfully connect only once; connectionless protocol sockets may use  connect  multiple
       times to change their association.  Connectionless sockets may dissolve the association by connecting to an address with the sa_family mem-
       ber of sockaddr set to AF_UNSPEC.

RETURN VALUE

       If the connection or binding succeeds, zero is returned.  On error, -1 is returned, and errno is set appropriately.

ERRORS

       The following are general socket errors only.  There may be other domain-specific error codes.

       EBADF  The file descriptor is not a valid index in the descriptor table.

       EFAULT The socket structure address is outside the user's address space.

       ENOTSOCK
	      The file descriptor is not associated with a socket.

       EISCONN
	      The socket is already connected.

       ECONNREFUSED
	      No one listening on the remote address.

       ETIMEDOUT
	      Timeout while attempting connection. The server may be too busy to accept new connections. Note that for IP sockets the timeout  may
	      be very long when syncookies are enabled on the server.

       ENETUNREACH
	      Network is unreachable.

       EADDRINUSE
	      Local address is already in use.

       EINPROGRESS
	      The  socket  is non-blocking and the connection cannot be completed immediately.	It is possible to select(2) or poll(2) for comple-
	      tion by selecting the socket for writing. After select indicates writability, use getsockopt(2) to read the SO_ERROR option at level
	      SOL_SOCKET  to  determine  whether connect completed successfully (SO_ERROR is zero) or unsuccessfully (SO_ERROR is one of the usual
	      error codes listed here, explaining the reason for the failure).

       EALREADY
	      The socket is non-blocking and a previous connection attempt has not yet been completed.

       EAGAIN No more free local ports or insufficient entries in the routing cache. For PF_INET see the  net.ipv4.ip_local_port_range	sysctl	in
	      ip(7) on how to increase the number of local ports.

       EAFNOSUPPORT
	      The passed address didn't have the correct address family in its sa_family field.

       EACCES, EPERM
	      The  user  tried to connect to a broadcast address without having the socket broadcast flag enabled or the connection request failed
	      because of a local firewall rule.

CONFORMING TO

       SVr4, 4.4BSD (the connect function first appeared in BSD 4.2).  SVr4 documents the additional general error  codes  EADDRNOTAVAIL,  EINVAL,
       EAFNOSUPPORT, EALREADY, EINTR, EPROTOTYPE, and ENOSR.  It also documents many additional error conditions not described here.

NOTE

       The  third  argument of connect is in reality an int (and this is what BSD 4.* and libc4 and libc5 have).  Some POSIX confusion resulted in
       the present socklen_t.  The draft standard has not been adopted yet, but glibc2 already	follows  it  and  also	has  socklen_t.  See  also
       accept(2).

BUGS

       Unconnecting a socket by calling connect with a AF_UNSPEC address is not yet implemented.

SEE ALSO

       accept(2), bind(2), listen(2), socket(2), getsockname(2)

Linux 2.2							    1998-10-03								CONNECT(2)