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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 connect() system call connects the socket referred to by  the  file
       descriptor  sockfd  to the address specified by serv_addr.  The addrlen
       argument specifies the size of serv_addr.  The format of the address in
       serv_addr  is determined by the address space of the socket sockfd; see
       socket(2) for further details.

       If the socket sockfd is  of  type  SOCK_DGRAM  then  serv_addr  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_SEQPACKET, this call attempts to make a connection
       to the socket that is bound to the address specified by serv_addr.

       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 member
       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.

       EACCES For Unix domain sockets, which are identified by pathname: Write
              permission is denied on the socket file, or search permission is
              denied for one of the directories in the path prefix.  (See also
              path_resolution(2).)

       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.

       EADDRINUSE
              Local address is already in use.

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

       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.

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

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

       ECONNREFUSED
              No one listening on the remote address.

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

       EINPROGRESS
              The   socket  is  non-blocking  and  the  connection  cannot  be
              completed immediately.  It is possible to select(2)  or  poll(2)
              for  completion  by  selecting  the  socket  for  writing. After
              select(2) 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).

       EINTR  The system call was interrupted by a signal that was caught.

       EISCONN
              The socket is already connected.

       ENETUNREACH
              Network is unreachable.

       ENOTSOCK
              The file descriptor is not associated with a socket.

       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.

CONFORMING TO

       SVr4, 4.4BSD (the connect() function first appeared in  4.2BSD).   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
       4.x BSD and libc4 and libc5 have).  Some POSIX  confusion  resulted  in
       the present socklen_t, also used by glibc.  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),  getsockname(2),  listen(2),   path_resolution(2),
       socket(2)