cc [ flag ... ] file ... –lsocket –lnsl [ library ... ] #include <sys/socket.h> int connect(int s, const struct sockaddr *name, socklen_t 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. 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.
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.
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.
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 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.
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 translating 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 not exist.
There were insufficient STREAMS resources available to complete the operation.
The server exited before the connection was complete.
Connection establishment timed out without establishing 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 IPC domain.
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: