initiate a connection on a socket
Standard C Library (libc, -lc)
, const struct
argument is a socket. If it is of type
, 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
, this call attempts to make a
connection to another socket. The other socket is specified by
, which is an address in the
communications space of the socket. Each communications space interprets the
argument in its own way. Generally,
stream sockets may successfully
only once; datagram sockets may use
() multiple times to change their
association. Datagram sockets may dissolve the association by connecting to an
invalid address, such as a null address.
() function returns the
value 0 if successful; otherwise the value -1 is returned and
the global variable errno
is set to indicate
() system call fails if:
- The s argument is not a valid
- The namelen argument is not a valid
length for the address family.
- The s argument is a descriptor for a
file, not a socket.
- The specified address is not available on this machine.
- Addresses in the specified address family cannot be used with this
- The socket is already connected.
- Connection establishment timed out without establishing a connection.
- The attempt to connect was forcefully rejected.
- The connection was reset by the remote host.
- The network is not reachable from this host.
- The remote host is not reachable from this host.
- The address is already in use.
- The name argument specifies an area
outside the process address space.
- 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.
- The connection attempt was interrupted by the delivery of a signal. The
connection will be established in the background, as in the case of
- A previous connection attempt has not yet been completed.
- 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.
- 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.last may alleviate
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.
- A component of the path prefix is not a directory.
- A component of a pathname exceeded 255 characters, or an entire path name
exceeded 1023 characters.
- The named socket does not exist.
- Search permission is denied for a component of the path prefix.
- Write access to the named socket is denied.
- Too many symbolic links were encountered in translating the pathname.
() system call appeared in