NAME

connect − initiate a connection on a socket

SYNOPSIS

#include <sys/types.h>

int connect(int s, addr_t name, int namelen);

DESCRIPTION

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 communications space of the socket.  Each communications 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. 

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. 

EAGAIN The socket is non-blocking and the connection cannot be completed immediately.  It is possible to select 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. 

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 the socket descriptor, and issue another socket call to obtain a new descriptor before attempting another connect call. 

ENETUNREACH The network is not reachable from this host. 

EADDRINUSE The address is already in use. 

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. 

EINTR System call returned due to interrupt. 

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

EOPNOTSUPP The socket is in the listen state. 

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). 

ENOSR There were insufficient STREAMS resources available to complete the operation. 

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. 

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. 

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

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

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

SEE ALSO

close(2), accept(3N), connect(3N), getsockname(3N), socket(3N). 

NOTES

The type of address structure passed to connect depends on the address family.  UNIX domain sockets (address family AF_UNIX) require a socketaddr_un structure as defined in sys/un.h; Internet domain sockets (address family AF_INET) require a sockaddr_in structure as defined in netinet/in.h.  Other address families may require other structures.  Use the structure appropriate to the address family; cast the structure address to a generic caddr_t in the call to ­connect and pass the size of the structure in the namelen argument.