start-up-server

Description

The start-up-server function starts a TCP server. Use process-kill to kill the server, and 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 using make-instance and communicate with the client. The server does not accept more connections until function returns, so normally it should create another light-weight process to handle the connection. However, the operating system typically provides a small queue of partially accepted connections, which prevents connection failure for new clients until the server is ready to accept more connections. If function is not specified the built-in Lisp listener server is used. See the examples section below.

If announce is a stream or t (denoting *standard-output* ), a message appears on the stream when the server is started.

If announce is a function it is called when the server is started. announce should take two arguments: socket and condition . socket is the socket used by the server: announce can therefore be used to record this socket. condition describes the error if there is one. announce can be called with socket nil and a condition only if error is nil . If the process is killed, announce is called with socket nil and condition nil .

The default for announce is nil , meaning there is no message.

If service is a string or positive integer, it 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 called SERVICES and is stored in the Windows directory, and on Windows NT it is the file


%SystemRoot%\system32\drivers\etc\SERVICES

If service is nil or 0, then start-up-server chooses a free port. The default value for service is "lispworks ".

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


(format nil "~S server" service)

The wait argument controls whether start-up-server waits for the server to start or returns immediately. When wait is non-nil and an error was signalled, process is nil and the error is returned in startup-condition Otherwise just one value, the server process, is returned. The default for wait is nil .

The error argument controls what happens if an error is signalled in the server thread. If error is nil then the thread is terminated. If error is non-nil then the debugger is entered. The default value for error is (not wait ) .

Note: some versions of MS Windows fail to detect the case where more than one server binds a given port, so an error will not be raised in this situation.

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 calls read . The client should send a string using Common Lisp 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 generates EOF 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*)

This is a client which uses the talk server:

(defun talking-to-myself ()

  (with-open-stream

      (talk (comm:open-tcp-stream "localhost"

                                  *talk-port*))

    (dolist (monolog

             '("Hello self."

               "Why don't you say something original?"

               "Talk to you later then.  Bye."))

      (write-line monolog talk)

      (force-output talk)

      (format t "I said: \"~A\"~%"

              monolog)

      (format t "Self replied: \"~A\"~%"

              (read-line talk nil nil)))))

(talking-to-myself)

=>

I said: "Hello self."

Self replied: "You sent: 'Hello self.'"

I said: "Why don't you say something original?"

Self replied: "You sent: 'Why don't you say something original?'"

I said: "Talk to you later then.  Bye."

Self replied: "You sent: 'Talk to you later then.  Bye.'"

This example illustrates a server which picks a free port and records the socket. The last form queries the socket for the port used.

(defvar *my-socket* nil)

(defun my-announce-function (socket condition)

  (if socket

      (setf *my-socket* socket)

    (my-log-error condition)))

(comm:start-up-server :service nil

                      :error nil

                      :announce 'my-announce-function)

(multiple-value-bind (address port)

    (comm:get-socket-address *my-socket*)

  port)

start-up-server

Function

Summary

Package

Signature

Arguments

Values

Description

Examples

See also