Scroll to navigation

Tcl_OpenTcpClient(3tcl) Tcl Library Procedures Tcl_OpenTcpClient(3tcl)
 


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.



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.



SEE ALSO

Tcl_OpenFileChannel(3tcl), Tcl_RegisterChannel(3tcl), vwait(3tcl)



KEYWORDS

client, server, TCP



  

    8.0
    Tcl