Tcl_OpenTcpClient(3tcl)
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 specify-
ing 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 allo-
cated at random.
const char *myaddr (in) A string specify-
ing the host name
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Tcl_OpenTcpClient(3) Tcl Library Procedures Tcl_OpenTcpClient(3)
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 asyn-
chronously to the
server.
ClientData sock (in) Platform-specific
handle for client
TCP socket.
Tcl_TcpAcceptProc *proc (in) Pointer to a pro-
cedure 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
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Tcl_OpenTcpClient(3) Tcl Library Procedures Tcl_OpenTcpClient(3)
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 com-
pletes successfully or fails. If the channel is in nonblock-
ing mode, the input or output operation will return immedi-
ately and a subsequent call to Tcl_InputBlocked on the chan-
nel 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 spe-
cial 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:
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Tcl_OpenTcpClient(3) Tcl Library Procedures Tcl_OpenTcpClient(3)
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 connec-
tions 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 descrip-
tor 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(3), Tcl_RegisterChannel(3), vwait(n)
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Tcl_OpenTcpClient(3) Tcl Library Procedures Tcl_OpenTcpClient(3)
KEYWORDS
client, server, TCP
Tcl Last change: 8.0 5
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