1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
|
;;; guile-websocket --- WebSocket client/server
;;; Copyright © 2015 David Thompson <davet@gnu.org>
;;; Copyright © 2021 Jan (janneke) Nieuwenhuizen <janneke@gnu.org>
;;;
;;; This file is part of guile-websocket.
;;;
;;; Guile-websocket is free software; you can redistribute it and/or modify
;;; it under the terms of the GNU Lesser General Public License as
;;; published by the Free Software Foundation; either version 3 of the
;;; License, or (at your option) any later version.
;;;
;;; Guile-websocket is distributed in the hope that it will be useful,
;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
;;; Lesser General Public License for more details.
;;;
;;; You should have received a copy of the GNU Lesser General Public
;;; License along with guile-websocket. If not, see
;;; <http://www.gnu.org/licenses/>.
;;; Commentary:
;;
;; WebSocket server.
;;
;;; Code:
(define-module (web socket server)
#:use-module (ice-9 match)
#:use-module (rnrs bytevectors)
#:use-module (rnrs io ports)
#:use-module (web request)
#:use-module (web response)
#:use-module (web uri)
#:use-module (web socket frame)
#:use-module (web socket utils)
#:export (make-server-socket
run-server))
;; See section 4.2 for explanation of the handshake.
(define (read-handshake-request client-socket)
"Read HTTP request from CLIENT-SOCKET that should contain the
headers required for a WebSocket handshake."
;; See section 4.2.1.
(read-request client-socket))
(define (make-handshake-response client-key)
"Return an HTTP response object for upgrading to a WebSocket
connection for the client whose key is CLIENT-KEY, a base64 encoded
string."
;; See section 4.2.2.
(let ((accept-key (make-accept-key (string-trim-both client-key))))
(build-response #:code 101
#:headers `((upgrade . ("websocket"))
(connection . (upgrade))
(sec-websocket-accept . ,accept-key)))))
(define* (make-server-socket #:key
(host #f)
(family AF_INET)
(addr (if host (inet-pton family host) INADDR_LOOPBACK))
(port 8080))
(let ((sock (socket PF_INET SOCK_STREAM 0)))
(setsockopt sock SOL_SOCKET SO_REUSEADDR 1)
(bind sock AF_INET addr port)
sock))
(define (accept-new-client server-socket)
(match (accept server-socket)
((client-socket . _) client-socket)))
(define (serve-client client-socket handler)
"Serve client connected via CLIENT-SOCKET by performing the HTTP
handshake and listening for control and data frames. HANDLER is
called for each complete message that is received."
(define (handle-data-frame type data)
(let* ((result (handler (match type
('text (utf8->string data))
('binary data))))
(response (cond
((string? result)
(make-text-frame result))
((bytevector? result)
(make-binary-frame result))
((not result)
#f))))
(when response
(write-frame response client-socket))))
(define (read-frame-maybe)
(and (not (port-eof? client-socket))
(read-frame client-socket)))
;; Perform the HTTP handshake and upgrade to WebSocket protocol.
(let* ((request (read-handshake-request client-socket))
(client-key (assoc-ref (request-headers request) 'sec-websocket-key))
(response (make-handshake-response client-key)))
(write-response response client-socket)
(let loop ((fragments '())
(type #f))
(let ((frame (read-frame-maybe)))
(cond
;; EOF - port is closed.
((not frame)
(close-port client-socket))
;; Per section 5.4, control frames may appear interspersed
;; along with a fragmented message.
((close-frame? frame)
;; Per section 5.5.1, echo the close frame back to the
;; client before closing the socket. The client may no
;; longer be listening.
(false-if-exception
(write-frame (make-close-frame (frame-data frame)) client-socket))
(close-port client-socket))
((ping-frame? frame)
;; Per section 5.5.3, a pong frame must include the exact
;; same data as the ping frame.
(write-frame (make-pong-frame (frame-data frame)) client-socket)
(loop fragments type))
((pong-frame? frame) ; silently ignore pongs
(loop fragments type))
((first-fragment-frame? frame) ; begin accumulating fragments
(loop (list frame) (frame-type frame)))
((final-fragment-frame? frame) ; concatenate all fragments
(handle-data-frame type (frame-concatenate (reverse fragments)))
(loop '() #f))
((fragment-frame? frame) ; add a fragment
(loop (cons frame fragments) type))
((data-frame? frame) ; unfragmented data frame
(handle-data-frame (frame-type frame) (frame-data frame))
(loop '() #f)))))))
(define* (run-server handler #:optional (server-socket (make-server-socket)))
"Run WebSocket server on SERVER-SOCKET. HANDLER, a procedure that
accepts a single argument, is called for each complete message that
the server receives from a client. When the message is in text
format, HANDLER is passed a string. When the message is in binary
format, HANDLER is passed a bytevector. HANDLER must return either a
string, bytevector, or #f. Strings and bytevectors are sent to the
client in response to their message, and #f indicates that nothing
should be sent back."
;; TODO: Handle multiple simultaneous clients.
(listen server-socket 1)
(sigaction SIGPIPE SIG_IGN)
(let loop ()
(serve-client (accept-new-client server-socket) handler)
(loop)))
|
