50 lines
1.9 KiB
Racket
50 lines
1.9 KiB
Racket
#lang scribble/manual
|
|
@require[racket/include]
|
|
@include{prelude.inc}
|
|
|
|
@title{Examples}
|
|
|
|
@section{TCP echo Server}
|
|
|
|
Here is a complete Marketplace program, @tt{examples/echo-paper.rkt}:
|
|
|
|
@#reader scribble/comment-reader (racketmod marketplace
|
|
|
|
(endpoint #:subscriber (tcp-channel ? (tcp-listener 5999) ?)
|
|
#:conversation (tcp-channel from to _)
|
|
#:on-presence (spawn #:child (echoer from to)))
|
|
|
|
(define (echoer from to)
|
|
(transition stateless
|
|
(endpoint #:subscriber (tcp-channel from to ?)
|
|
#:on-absence (quit)
|
|
[(tcp-channel _ _ data)
|
|
(send-message (tcp-channel to from data))])))
|
|
)
|
|
|
|
The top-level @racket[endpoint] action subscribes to TCP connections
|
|
arriving on port 5999, and @racket[spawn]s a fresh process in response to
|
|
each (@racket[#:on-presence]). The topic of
|
|
conversation (@racket[#:conversation]) associated with the newly-present
|
|
subscription is analyzed to give the remote
|
|
(@racket[from]) and local (@racket[to]) TCP addresses, which are
|
|
passed to the @racket[echoer] function to give the initial actions for
|
|
the corresponding process. Here, the process is stateless, using the
|
|
special constant @racket[stateless] as its state.
|
|
|
|
Each connection's process creates an endpoint subscribing to data
|
|
arriving on its particular connection, using @racket[from] and @racket[to]
|
|
passed in from the top-level @racket[endpoint]. When data arrives, it is
|
|
echoed back to the remote peer using @racket[send-message]. Presence
|
|
manages disconnection; when the remote peer closes the TCP connection,
|
|
the @racket[#:on-absence] handler in @racket[echoer] issues a @racket[quit]
|
|
action, terminating the connection's process. The heart of our system
|
|
is the interface between a process and its containing VM. Our
|
|
implementation instantiates this interface as a collection of Typed
|
|
Racket programs.
|
|
|
|
@section{TCP chat server}
|
|
@section{Authoritative DNS server}
|
|
@section{DNS resolver server}
|
|
@section{SSH server}
|