connect

- connect a socket

Synopsis

cc [ flag ... ] file ... -lsocket -lnsl [ library ... ]
#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, 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. This behavior can be modified by the SO_PASSIVE_CONNECT socket option provided by setsockopt(3SOCKET). The other socket is specified by name, which is an address in the communication 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. Generally, 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 address.

Return Values

If the connection or binding succeeds, 0 is returned. Otherwise, -1 is returned, errno is set to indicate the error, and state of the socket is unspecified. Applications should close the file descriptor and create a new socket before attempting to reconnect.

Errors

The call fails if:

EACCES

Search permission is denied for a component of the path prefix of the pathname in name.

EADDRINUSE

The address is already in use.

EADDRNOTAVAIL

The specified address is not available.

EAFNOSUPPORT

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

EALREADY

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

EBADF

s is not a valid descriptor.

ECONNREFUSED

The attempt to connect was forcefully rejected.

EINPROGRESS

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 writing.

EINTR

The connection attempt was interrupted before any data arrived by the delivery of a signal. The connection, however, will be established asynchronously.

EINVAL

namelen is not the size of a valid address for the specified address family.

EIO

An I/O error occurred while reading from or writing to the file system.

EISCONN

The socket is already connected.

ELOOP

Too many symbolic links were encountered in translating the pathname in name.

ENETUNREACH

The network is not reachable from this host.

EHOSTUNREACH

The remote host is not reachable from this host.

ENOENT

A component of the path prefix of the pathname in name does not exist.

ENOENT

The socket referred to by the pathname in name does not exist.

ENOSR

There were insufficient STREAMS resources available to complete the operation.

ENXIO

The server exited before the connection was complete.

ETIMEDOUT

Connection establishment timed out without establishing a connection.

EWOULDBLOCK

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 IPC domain.

ENOTDIR

A component of the path prefix of the pathname in name is not a directory.

ENOTSOCK

s is not a socket.

ENOTSOCK

name is not a socket.

EPROTOTYPE

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.

Attributes

See attributes(5) for descriptions of the following attributes:

See Also

close(2), accept(3SOCKET), getsockname(3SOCKET), select(3C), setsockopt(3SOCKET), socket(3SOCKET), socket.h(3HEAD), attributes(5)