connect(3N) manual page
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connect - initiate a connection on a socket
cc [ flag ... ]
file ... -lsocket -lnsl [ library ... ]
#include <sys/types.h>
#include <sys/socket.h>
int connect(int s, struct sockaddr *name, int namelen);
Safe
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; it 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 communication space of the
socket. Each communication space interprets the name parameter in its own
way. If s is not bound, then it will be bound to an address selected by
the underlying transport provider. Generally, stream sockets may successfully
connect() only once; datagram sockets may use connect() multiple times
to change their association. Datagram sockets may dissolve the association
by connecting to a null address.
If the connection or binding
succeeds, 0 is returned. Otherwise, -1 is returned and sets errno to indicate
the error.
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 on the remote machine.
- 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. The calling program should close(2)
the socket
descriptor, and issue another socket(3N)
call to obtain a new descriptor
before attempting another connect() call.
- EINPROGRESS
- The socket is non-blocking and the connection cannot be completed
immediately. It is possible to select(3C)
for completion by selecting the
socket for writing. However, this is only possible if the socket STREAMS
module is the topmost module on the protocol stack with a write service
procedure. This will be the normal case.
- EINTR
- The connection attempt was interrupted before any data arrived
by the delivery of a signal.
- 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.
- 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.
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.
- 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 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).
close(2)
, accept(3N)
, getsockname(3N)
, select(3C)
, socket(3N)
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