CONNECT(3SOCKET)CONNECT(3SOCKET)NAMEconnect - initiate a connection on a socket
cc [ flag ... ] file ... -lsocket-lnsl [ library ... ]
int connect(int s, const struct sockaddr *name, int namelen);
The parameter s is a socket. If it is of type SOCK_DGRAM, connect()
specifies the peer with which the socket is to be associated. This
address is the address to which datagrams are to be sent if a receiver
is not explicitly designated. This address is the only address from
which datagrams are to be received. If the socket s is of type
SOCK_STREAM, connect() attempts to make a connection to another socket.
The other socket is specified by name. name is an address in the commu‐
nication space of the socket. Each communication space interprets the
name parameter in its own way. If s is not bound, then s will be bound
to an address selected by the underlying transport provider. Gener‐
ally, stream sockets can successfully connect() only once. Datagram
sockets can use connect() multiple times to change their association.
Datagram sockets can dissolve the association by connecting to a null
If the connection or binding succeeds, 0 is returned. Otherwise, −1 is
returned and sets errno to indicate the error.
The call fails if:
Search permission is denied for a component of the
path prefix of the pathname in name.
The address is already in use.
The specified address is not available on the remote
Addresses in the specified address family cannot be
used with this socket.
The socket is non-blocking, and a previous connection
attempt has not yet been completed.
s is not a valid descriptor.
The attempt to connect was forcefully rejected. The
calling program should close(2) the socket descriptor,
and issue another socket(3SOCKET) call to obtain a new
descriptor before attempting another connect() call.
The socket is non-blocking, and the connection cannot
be completed immediately. You can use select(3C) to
complete the connection by selecting the socket for
The connection attempt was interrupted before any data
arrived by the delivery of a signal. The connection,
however, will be established asynchronously.
namelen is not the size of a valid address for the
specified address family.
An I/O error occurred while reading from or writing to
the file system.
The socket is already connected.
Too many symbolic links were encountered in translat‐
ing the pathname in name.
The network is not reachable from this host.
The remote host is not reachable from this host.
A component of the path prefix of the pathname in name
does not exist.
The socket referred to by the pathname in name does
There were insufficient STREAMS resources available to
complete the operation.
The server exited before the connection was complete.
Connection establishment timed out without establish‐
ing a connection.
The socket is marked as non-blocking, and the
requested operation would block.
The following errors are specific to connecting names in the UNIX
domain. These errors might not apply in future versions of the UNIX
A component of the path prefix of the pathname in name is
not a directory.
s is not a socket.
name is not a socket.
The file that is referred to by name is a socket of a
type other than type s. For example, s is a SOCK_DGRAM
socket, while name refers to a SOCK_STREAM socket.
See attributes(5) for descriptions of the following attributes:
│ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
│MT-Level │ Safe │
SEE ALSOclose(2), accept(3SOCKET), getsockname(3SOCKET), select(3C),
socket(3SOCKET), socket.h(3HEAD), attributes(5)
Mar 08, 2005 CONNECT(3SOCKET)