NAME

       connect — initiate a connection on a socket

LIBRARY

       Standard C Library (libc, -lc)

SYNOPSIS

       #include <sys/socket.h>

       int
       connect(int s, const struct sockaddr *name, socklen_t namelen);

DESCRIPTION

       The  s  argument  is  a socket.  If it is of type 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 SOCK_STREAM, this call attempts to
       make a connection to another socket.  The other socket is specified by name, which is an address  in  the
       communications  space of the socket.  namelen indicates the amount of space pointed to by name, in bytes;
       the sa_len member of name is ignored.  Each communications space interprets the name argument in its  own
       way.   Generally, stream sockets may successfully connect() only once; datagram sockets may use connect()
       multiple times to change their association.  Datagram sockets may dissolve the association by  connecting
       to an invalid address, such as a null address.

RETURN VALUES

       The  connect()  function  returns  the  value 0 if successful; otherwise the value -1 is returned and the
       global variable errno is set to indicate the error.

ERRORS

       The connect() system call fails if:

       [EBADF]            The s argument is not a valid descriptor.

       [EINVAL]           The namelen argument is not a valid length for the address family.

       [ENOTSOCK]         The s argument is a descriptor for a file, not a socket.

       [EADDRNOTAVAIL]    The specified address is not available on this machine.

       [EAFNOSUPPORT]     Addresses in the specified address family cannot be used with this socket.

       [EISCONN]          The socket is already connected.

       [ETIMEDOUT]        Connection establishment timed out without establishing a connection.

       [ECONNREFUSED]     The attempt to connect was forcefully rejected.

       [ECONNRESET]       The connection was reset by the remote host.

       [ENETUNREACH]      The network is not reachable from this host.

       [EHOSTUNREACH]     The remote host is not reachable from this host.

       [EADDRINUSE]       The address is already in use.

       [EFAULT]           The name argument specifies an area outside the process address space.

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

       [EINTR]            The  connection  attempt  was interrupted by the delivery of a signal.  The connection
                          will be established in the background, as in the case of EINPROGRESS.

       [EALREADY]         A previous connection attempt has not yet been completed.

       [EACCES]           An  attempt  is  made  to  connect  to  a  broadcast  address  (obtained  through  the
                          INADDR_BROADCAST  constant or the INADDR_NONE return value) through a socket that does
                          not provide broadcast functionality.

       [EAGAIN]           An auto-assigned port number was requested but no auto-assigned ports  are  available.
                          Increasing    the    port    range    specified    by    sysctl(3)    MIB    variables
                          net.inet.ip.portrange.first and net.inet.ip.portrange.last may alleviate the problem.

       The following errors are specific to connecting names in the UNIX domain.  These errors may not apply  in
       future versions of the UNIX IPC domain.

       [ENOTDIR]          A component of the path prefix is not a directory.

       [ENAMETOOLONG]     A  component  of  a  pathname exceeded 255 characters, or an entire path name exceeded
                          1023 characters.

       [ENOENT]           The named socket does not exist.

       [EACCES]           Search permission is denied for a component of the path prefix.

       [EACCES]           Write access to the named socket is denied.

       [ELOOP]            Too many symbolic links were encountered in translating the pathname.

       [EPERM]            Write access to the named socket is denied.

SEE ALSO

       accept(2), getpeername(2), getsockname(2), select(2), socket(2), sysctl(3), sysctl(8)

HISTORY

       The connect() system call appeared in 4.2BSD.

Debian                                           August 18, 2016                                      CONNECT(2)