connect(2) - NetBSD Manual Pages

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CONNECT(2)                NetBSD System Calls Manual                CONNECT(2)


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 parameter s 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 commu-
     nications space of the socket.  namelen indicates the amount of space
     pointed to by name, in bytes.  Each communications space interprets the
     name parameter in its own way.  Generally, stream sockets may success-
     fully 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.

     If a connect() call is interrupted by a signal, it will return with errno
     set to EINTR and the connection attempt will proceed as if the socket was
     non-blocking.  Subsequent calls to connect() will set errno to EALREADY.


RETURN VALUES

     If the connection or binding succeeds, 0 is returned.  Otherwise a -1 is
     returned, and a more specific error code is stored in errno.


ERRORS

     The connect() call fails if:

     [EBADF]            s is not a valid descriptor.

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

     [EINVAL]           The socket address length passed was outside the
                        allowable range.

     [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 establish-
                        ing a connection.

     [ECONNREFUSED]     The attempt to connect was forcefully rejected.

     [ENETUNREACH]      The network isn't reachable from this host.

     [EADDRINUSE]       The address is already in use.

     [EFAULT]           The name parameter 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)
                        or poll(2) for completion by selecting or polling the
                        socket for writing.  The success or failure of the
                        connect operation may be determined by using
                        getsockopt(2) to read the socket error status with the
                        SO_ERROR option at the SOL_SOCKET level.  The returned
                        socket error status is zero on success, or one of the
                        error codes listed here on failure.

     [EALREADY]         Either the socket is non-blocking mode or a previous
                        call to connect() was interrupted by a signal, and the
                        connection attempt has not yet been completed.

     [EINTR]            The connection attempt was interrupted by a signal.

     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 {NAME_MAX} charac-
                        ters, or an entire path name exceeded {PATH_MAX} char-
                        acters.

     [ENOENT]           The named socket does not exist.

     [EACCES]           Search permission is denied for a component of the
                        path prefix, or write access to the named socket is
                        denied.

     [ELOOP]            Too many symbolic links were encountered in translat-
                        ing the pathname.


SEE ALSO

     accept(2), getsockname(2), getsockopt(2), poll(2), select(2), socket(2)


HISTORY

     The connect() function call appeared in 4.2BSD.

NetBSD 10.1                     March 27, 2021                     NetBSD 10.1