Tribblix: manual page: Tcl_MakeTcpClientChannel.3

Tcl_OpenTcpClient(3) Tcl Library Procedures Tcl_OpenTcpClient(3)

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NAME

Tcl_OpenTcpClient, Tcl_MakeTcpClientChannel, Tcl_OpenTcpServer -
procedures to open channels using TCP sockets

SYNOPSIS

#include <tcl.h>

Tcl_Channel
Tcl_OpenTcpClient(interp, port, host, myaddr, myport, async)

Tcl_Channel
Tcl_MakeTcpClientChannel(sock)

Tcl_Channel
Tcl_OpenTcpServer(interp, port, myaddr, proc, clientData)

ARGUMENTS

Tcl_Interp *interp (in) Tcl interpreter to use for
error reporting. If non-
NULL and an error occurs,
an error message is left
in the interpreter's
result.

int port (in) A port number to connect
to as a client or to
listen on as a server.

const char *host (in) A string specifying a host
name or address for the
remote end of the
connection.

int myport (in) A port number for the
client's end of the
socket. If 0, a port
number is allocated at
random.

const char *myaddr (in) A string specifying the
host name or address for
network interface to use
for the local end of the
connection. If NULL, a
default interface is
chosen.

int async (in) If nonzero, the client
socket is connected
asynchronously to the
server.

ClientData sock (in) Platform-specific handle
for client TCP socket.

Tcl_TcpAcceptProc *proc (in) Pointer to a procedure to
invoke each time a new
connection is accepted via
the socket.

ClientData clientData (in) Arbitrary one-word value
to pass to proc.
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DESCRIPTION

These functions are convenience procedures for creating channels that
communicate over TCP sockets. The operations on a channel are
described in the manual entry for Tcl_OpenFileChannel.

TCL_OPENTCPCLIENT
Tcl_OpenTcpClient opens a client TCP socket connected to a port on a
specific host, and returns a channel that can be used to communicate
with the server. The host to connect to can be specified either as a
domain name style name (e.g. www.sunlabs.com), or as a string
containing the alphanumeric representation of its four-byte address
(e.g. 127.0.0.1). Use the string localhost to connect to a TCP
socket on the host on which the function is invoked.

The myaddr and myport arguments allow a client to specify an address
for the local end of the connection. If myaddr is NULL, then an
interface is chosen automatically by the operating system. If myport
is 0, then a port number is chosen at random by the operating system.

If async is zero, the call to Tcl_OpenTcpClient returns only after
the client socket has either successfully connected to the server, or
the attempted connection has failed. If async is nonzero the socket
is connected asynchronously and the returned channel may not yet be
connected to the server when the call to Tcl_OpenTcpClient returns.
If the channel is in blocking mode and an input or output operation
is done on the channel before the connection is completed or fails,
that operation will wait until the connection either completes
successfully or fails. If the channel is in nonblocking mode, the
input or output operation will return immediately and a subsequent
call to Tcl_InputBlocked on the channel will return nonzero.

The returned channel is opened for reading and writing. If an error
occurs in opening the socket, Tcl_OpenTcpClient returns NULL and
records a POSIX error code that can be retrieved with Tcl_GetErrno.
In addition, if interp is non-NULL, an error message is left in the
interpreter's result.

The newly created channel is not registered in the supplied
interpreter; to register it, use Tcl_RegisterChannel. If one of the
standard channels, stdin, stdout or stderr was previously closed, the
act of creating the new channel also assigns it as a replacement for
the standard channel.

TCL_MAKETCPCLIENTCHANNEL
Tcl_MakeTcpClientChannel creates a Tcl_Channel around an existing,
platform specific, handle for a client TCP socket.

The newly created channel is not registered in the supplied
interpreter; to register it, use Tcl_RegisterChannel. If one of the
standard channels, stdin, stdout or stderr was previously closed, the
act of creating the new channel also assigns it as a replacement for
the standard channel.

TCL_OPENTCPSERVER
Tcl_OpenTcpServer opens a TCP socket on the local host on a specified
port and uses the Tcl event mechanism to accept requests from clients
to connect to it. The myaddr argument specifies the network
interface. If myaddr is NULL the special address INADDR_ANY should
be used to allow connections from any network interface. Each time a
client connects to this socket, Tcl creates a channel for the new
connection and invokes proc with information about the channel. Proc
must match the following prototype:

typedef void Tcl_TcpAcceptProc(
ClientData clientData,
Tcl_Channel channel,
char *hostName,
int port);

The clientData argument will be the same as the clientData argument
to Tcl_OpenTcpServer, channel will be the handle for the new channel,
hostName points to a string containing the name of the client host
making the connection, and port will contain the client's port
number. The new channel is opened for both input and output. If
proc raises an error, the connection is closed automatically. Proc
has no return value, but if it wishes to reject the connection it can
close channel.

Tcl_OpenTcpServer normally returns a pointer to a channel
representing the server socket. If an error occurs,
Tcl_OpenTcpServer returns NULL and records a POSIX error code that
can be retrieved with Tcl_GetErrno. In addition, if the interpreter
is non-NULL, an error message is left in the interpreter's result.

The channel returned by Tcl_OpenTcpServer cannot be used for either
input or output. It is simply a handle for the socket used to accept
connections. The caller can close the channel to shut down the
server and disallow further connections from new clients.

TCP server channels operate correctly only in applications that
dispatch events through Tcl_DoOneEvent or through Tcl commands such
as vwait; otherwise Tcl will never notice that a connection request
from a remote client is pending.

The newly created channel is not registered in the supplied
interpreter; to register it, use Tcl_RegisterChannel. If one of the
standard channels, stdin, stdout or stderr was previously closed, the
act of creating the new channel also assigns it as a replacement for
the standard channel.

PLATFORM ISSUES

On Unix platforms, the socket handle is a Unix file descriptor as
returned by the socket system call. On the Windows platform, the
socket handle is a SOCKET as defined in the WinSock API.

KEYWORDS