3 The COMM package

start-up-server

Function

Summary

Starts a TCP server.

Package

comm

Signature

start-up-server &key function announce service process-name =>

Arguments

function: A function name.
announce: A keyword.
service: An integer or string.
process-name: A symbol or expression.

Values

None.

Description

Thestart-up-server function starts a TCP server. Usemp:process-kill to kill the server, andcomm:open-tcp-stream to send messages from another client to the server.

The function argument provides the name of the function that processes connections. When a connection is made function is called with the connected socket handle, at which point you can make a stream usingmake-instance and communicate with the client. The server does not accept more connections until function returns, so normally it creates another light-weight process to handle the connection. If no function is specified the built-in Lisp listener server is used. See the examples section below.

The announce keyword causes a message to appear when the server is started. The value of this keyword is the stream to which the startup message is displayed.

The service argument specifies the name of the service. The location of the file specifying the names of services available varies, but typically on Windows 95 it is calledSERVICES and is stored in theWindows directory., and on Windows NT it is the file

%SystemRoot%\system32\drivers\etc\SERVICES

: The default value for service islispworks.
: The process-name specifies the process name. The default is constructed from the service name in the following fashion:

(format nil "~S server" service)

Examples
: The following example uses the built-in Lisp listener server:

(comm:start-up-server :service 10243)

: It makes a Lisp listener server on port 10243 (check with local network managers that this port number is safe to use). When a client connects to this, Lisp callsREAD. The client should send a string using CL syntax followed by a newline. This string is used to name a new light-weight process that runs a Lisp listener. When this has been created, the server waits for more connections.
: The next example illustrates the use of the function argument. For each line of input read by the server it writes the line back with a message. The stream generatesEOF if the other end closes the connection.

(defvar *talk-port* 10244)  ; a free TCP port number

(defun make-stream-and-talk (handle)
  (let ((stream (make-instance 'comm:socket-stream
                               :socket handle
                               :direction :io
                               :element-type
                                  'base-char)))
  (mp:process-run-function (format nil "talk ~D"
                                   handle)
                           '()
                           'talk-on-stream stream)))

(defun talk-on-stream (stream)
  (unwind-protect
      (loop for line = (read-line stream nil nil)
            while line
            do
            (format stream "You sent: '~A'~%" line)
            (force-output stream))
      (close stream)))

(comm:start-up-server :function 'make-stream-and-talk
                      :service *talk-port*)

See also
: open-tcp-stream
socket-stream