CONNECT(2) — SYSTEM CALLS

NAME

connect − initiate a connection on a socket

SYNOPSIS

#include <sys/types.h>
#include <sys/socket.h>

connect(s, name, namelen)
int s;
struct sockaddr ∗name;
int namelen;

DESCRIPTION

The parameter s is a socket. If it is of type SOCK_DGRAM, then 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 it is of type SOCK_STREAM, then this call attempts to make a connection to another socket. The other socket is specified by name which is an address in the communications space of the socket. Each communications space interprets the name parameter in its own way. 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 an invalid address, such as a null address.

RETURN VALUE

If the connection or binding succeeds, then 0 is returned. Otherwise a −1 is returned, and a more specific error code is stored in errno.

ERRORS

The call fails if:

EBADF s is not a valid descriptor.

ENOTSOCK s is a descriptor for a file, not a socket.

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

EADDRNOTAVAIL The specified address is not available on the remote machine.

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

EISCONN The socket is already connected.

ETIMEDOUT Connection establishment timed out without establishing a connection.

ECONNREFUSED The attempt to connect was forcefully rejected. The calling program should close(2) the socket descriptor, and issue another socket(2) call to obtain a new descriptor before attempting another connect(2) call.

ENETUNREACH The network is not reachable from this host.

EADDRINUSE The address is already in use.

EFAULT The name parameter specifies an area outside the process address space.

EINPROGRESS The socket is non-blocking and the connection cannot be completed immediately. It is possible to select(2) for completion by selecting the socket for writing.

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

EINTR The connection attempt was interrupted before any data arrived by the delivery of a signal.

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 path name in name is not a directory.

ENAMETOOLONG The length of a component of the path name in name exceeds 255 characters, or the length of the entire path name in name exceeds 1023 characters.

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

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

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

ELOOP Too many symbolic links were encountered in translating the path name in name.

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

ENOTSOCK The file referred to by name is not a socket.

EPROTOTYPE The file referred to by name is a socket of a type other than the type of s (e.g., s is a SOCK_DGRAM socket, while name refers to a SOCK_STREAM socket).

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