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.
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.
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.
SEE ALSO¶
Tcl_OpenFileChannel(3tcl), Tcl_RegisterChannel(3tcl), vwait(3tcl)
KEYWORDS¶
channel, client, server, socket, TCP