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a network client

From: Catonano
Subject: a network client
Date: Thu, 13 Dec 2018 09:17:56 +0100

I wrote a small server in Guile scheme

I used the command "nc" to test it

It seems to work

Then I wrote a small client in Guile

It doesn't work and I don't understand why

At the REPL:

scheme@(lsp-client)> (run-ping-test 11211)

This runs the client

The client is supposed to write a short string on the socket connected to
the server  and then read the serverÅ› reply from the same socket

But instead nothing happens

It doesn't return the prompt and the server doesn't receive any string

I know this because the server displays the string it receives on the
terminal, when it receives it

and it this case it doesn't display anything

So I interrupt the client with CTRL-C (2 times as one time seems to not

^C^CERROR: In procedure scm-error:
User interrupt

Entering a new prompt.  Type `,bt' for a backtrace or `,q' to continue.
scheme@(lsp-client) [1]> ,q

at this point I quit Guile, like this

scheme@(lsp-client)> ,q

At this point the sever DOES display the short string on the terminal !!

It seems that the client writes the string on the socket only when I close
the Guile process

Now, this is the client:

(define* (client  addrinfo #:key (request-port 11211))
  (let ((port (connect-to-server addrinfo)))
    (put-string port "hello")
    (put-char port #\newline)
    (force-output port)
    (let ((line (read-line port)))
    (display line)

Instead, with the following simplified version, the server receives the
string and "run-ping-test" returns a value and the prompt

(define* (client  addrinfo #:key (request-port 11211))
  (let ((port (connect-to-server addrinfo)))
    (put-string port "hello")
    (put-char port #\newline)
    (force-output port)
    (close-port port) ;;<-- this was not present in the previous version !!

So it seems that in order to write on the socket you need to call

But if the client closes the port, how can it receive a reply from the
server ?

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