connect - initiate a connection on a socket
int connect(int sockfd, struct sockaddr *serv_addr, int
The parameter sockfd is a socket. If the socket 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
serv_addr, which is an address in the communications space
of the socket. Each communications space interprets the
serv_addr parameter in its own way. Generally, stream
sockets may successfully connect only once; datagram sock
ets may use connect multiple times to change their associ
ation. Datagram sockets may dissolve the association by
connecting to an address with the sa_family sockaddr mem
ber set to AF_UNSPEC.
If the connection or binding succeeds, zero is returned.
On error, -1 is returned, and errno is set appropriately.
The following are general socket errors only. There may
be other domain-specific error codes.
EBADF Bad descriptor.
EFAULT The socket structure address is outside the user's
The descriptor is not associated with a socket.
EISCONN The socket is already connected.
Connection refused at server.
Timeout while attempting connection.
Network is unreachable.
Address is already in use.
The socket is non-blocking and the connection can
not be completed immediately. It is possible to
select(2) or poll(2) for completion by selecting
the socket for writing. After select indicates
writability, use getsockopt(2) to read the
SO_ERROR option at level SOL_SOCKET to determine
whether connect completed successfully (SO_ERROR
is zero) or unsuccessfully (SO_ERROR is one of the
usual error codes listed above, explaining the
reason for the failure).
The socket is non-blocking and a previous connec
tion attempt has not yet been completed.
The passed address didn't have the correct address
family in its sa_family field.
EACCES The user tried to connect to a broadcast address
without having the socket broadcast flag enabled.
SVr4, 4.4BSD (the connect function first appeared in BSD
4.2). SVr4 documents the additional general error codes
EADDRNOTAVAIL, EINVAL, EAFNOSUPPORT, EALREADY, EINTR,
EPROTOTYPE, and ENOSR. It also documents many additional
error conditions not described here.
accept(2), bind(2), listen(2), socket(2), getsockname(2)