Originální popis anglicky:
connect - initiate a connection on a socket
Návod, kniha: Linux Programmer's Manual
#include <sys/types.h>
#include <sys/socket.h>
int connect(int sockfd, const struct sockaddr
*serv_addr, socklen_t addrlen);
The file descriptor
sockfd must refer to a socket. If the socket is of
type
SOCK_DGRAM then the
serv_addr address is the address to
which datagrams are sent by default, and the only address from which datagrams
are received. If the socket is of type
SOCK_STREAM or
SOCK_SEQPACKET, this call attempts to make a connection to another
socket. The other socket is specified by
serv_addr, which is an address
(of length
addrlen) in the communications space of the socket. Each
communications space interprets the
serv_addr parameter in its own way.
Generally, connection-based protocol sockets may successfully
connect
only once; connectionless protocol sockets may use
connect multiple
times to change their association. Connectionless sockets may dissolve the
association by connecting to an address with the
sa_family member of
sockaddr 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.
- EACCES
- For Unix domain sockets, which are identified by pathname:
Write permission is denied on the socket file, or search permission is
denied for one of the directories in the path prefix. (See also
path_resolution(2).)
- EACCES, EPERM
- The user tried to connect to a broadcast address without
having the socket broadcast flag enabled or the connection request failed
because of a local firewall rule.
- EADDRINUSE
- Local address is already in use.
- EAFNOSUPPORT
- The passed address didn't have the correct address family
in its sa_family field.
- EAGAIN
- No more free local ports or insufficient entries in the
routing cache. For PF_INET see the
net.ipv4.ip_local_port_range sysctl in ip(7) on how to
increase the number of local ports.
- EALREADY
- The socket is non-blocking and a previous connection
attempt has not yet been completed.
- EBADF
- The file descriptor is not a valid index in the descriptor
table.
- ECONNREFUSED
- No one listening on the remote address.
- EFAULT
- The socket structure address is outside the user's address
space.
- EINPROGRESS
- The socket is non-blocking and the connection cannot 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
here, explaining the reason for the failure).
- EISCONN
- The socket is already connected.
- ENETUNREACH
- Network is unreachable.
- ENOTSOCK
- The file descriptor is not associated with a socket.
- ETIMEDOUT
- Timeout while attempting connection. The server may be too
busy to accept new connections. Note that for IP sockets the timeout may
be very long when syncookies are enabled on the server.
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.
The third argument of
connect is in reality an int (and this is what BSD
4.* and libc4 and libc5 have). Some POSIX confusion resulted in the present
socklen_t, also used by glibc. See also
accept(2).
Unconnecting a socket by calling
connect with a
AF_UNSPEC address
is not yet implemented.
accept(2),
bind(2),
getsockname(2),
listen(2),
path_resolution(2),
socket(2)
