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Bigloo defines sockets, on systems that support them, as first class objects.
Sockets permits processes to communicate even if they are on different
machines. Sockets are useful for creating client-server applications.
The implementation and this documentation are, to a great
extent copies of the STk [Gallesio95] socket support.
make-client-socket hostname port-number [buffered] | bigloo procedure |
make-client-socket returns a new socket object. This socket establishes
a link between the running application listening on port port-number
of hostname . If optional argument buffered is #f then
the input port associated with the socket is unbuffered. This is useful for
socket clients connected to servers that do not emit #\Newline character
after emissions. If optional argument buffered is missing or is not
to #f the input port uses a buffer.
When a socket is used in unbufferized mode the characters available on
the input port must be read exclusively with read-char
or read-line . It is forbidden to use read or any regular
grammar. This limitation is imposed by Rgc (see Regular Parsing) that
intrinsicly associate buffers with regular grammars. If the current Rgc
implementation is improved on the coming version this restriction will
be suppressed.
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socket? obj | bigloo procedure |
socket-server? obj | bigloo procedure |
socket-client? obj | bigloo procedure |
Returns #t if obj is a socket, a socket server a socket client.
Otherwise returns #f . Socket servers and socket clients are
sockets.
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socket-hostname socket | bigloo procedure |
Returns a string which contains the name of the distant host attached to
socket . If socket has been created with make-client-socket
this procedure returns the official name of the distant machine used for
connection. If socket has been created with make-server-socket ,
this function returns the official name of the client connected to the socket.
If no client has used yet the socket, this function returns #f .
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socket-host-address socket | bigloo procedure |
Returns a string which contains the IP number of
the distant host attached to socket . If socket has been
created with make-client-socket this procedure returns the
IP number of the distant machine used for connection. If
socket has been created with make-server-socket , this
function returns the address of the client connected to the
socket. If no client has used yet the socket, this function returns
#f .
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socket-local-address socket | bigloo procedure |
Returns a string which contains the IP number of
the local host attached to socket .
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socket-port-number socket | bigloo procedure |
Returns the integer number of the port used for socket .
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socket-input socket | bigloo procedure |
socket-output socket | bigloo procedure |
Returns the file port associated for reading or writing with the program
connected with socket . If no connection has already been established,
these functions return #f .
The following example shows how to make a client socket. Here we create a
socket on port 13 of the machine ``kaolin.unice.fr ''
is generally used for testing: making a connection to it permits to know
the distant system's idea of the time of day.1:
(let ((s (make-client-socket "kaolin.unice.fr" 13)))
(print "Time is: " (read-line (socket-input s)))
(socket-shutdown s))
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make-server-socket [port-number] | bigloo procedure |
make-server-socket returns a new socket object. If port-number
is specified, the socket is listening on the specified port; otherwise, the
communication port is choosen by the system.
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socket-accept socket [buffered] | bigloo procedure |
The function socket-accept replaces the former Bigloo functions
socket-accept-connection and socket-dup .
socket-accept waits for a client connection on the given
socket . It returns a client-socket . If no client is
already waiting for a connection, this procedure blocks its caller;
otherwise, the first connection request on the queue of pending
connections is connected to socket . This procedure must be
called on a server socket created with make-server-socket . If
optional argument buffered is #f then the input port
associated with the socket is unbuffered. This is useful for socket
clients connected to servers that do not emit #\Newline character
after emissions. If optional argument buffered is missing or is
not to #f the input port uses a buffer. The result of
socket-accept is undefined.
Note: When a socket is used in unbufferized mode the characters
available on the input port must be read exclusively with
read-char or read-line . It is forbidden to use read
or any regular grammar. This limitation is imposed by Rgc (see
Regular Parsing) that intrinsicly associate buffers with regular
grammars. If the current Rgc implementation is improved on the coming
version this restriction will be suppressed.
The following exemple is a simple server which waits for a connection
on the port 1234
listening socket with the telnet command. With the given
example, this can be
achived by typing the following command in a window shell:
$ telnet localhost 1234 2. Once the connection with the
distant program is established, we read a line on the input port
associated to the socket and we write the length of this line on its
output port.
(let* ((s (make-server-socket 1234))
(s2 (socket-accept s)))
(let ((l (read-line (socket-input s2))))
(fprint (socket-output s) "Length is: " (string-length l))
(flush-output-port (socket-output s2)))
(socket-close s)
(socket-shutdown s))
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socket-accept-connection socket [buffered] | bigloo procedure |
socket-accept-connection waits for a client connection on the
given socket . If no client is already waiting for a connection,
this procedure blocks its caller; otherwise, the first connection
request on the queue of pending connections is connected to
socket .
note:This function is part of the old Bigloo API. It was
intended to be used in conjunction with
socket-accept-connection . The new API made of
socket-accept and socket-close should be preferred.
This procedure must be called on a server socket created
with make-server-socket . If optional argument buffered is
#f then the input port associated with the socket is
unbuffered. This is useful for socket clients connected to servers that
do not emit #\Newline character after emissions. If optional argument
buffered is missing or is not to #f the input port uses a
buffer. The result of socket-accept-connection is undefined.
Note: When a socket is used in unbufferized mode the characters
available on the input port must be read exclusively with
read-char or read-line . It is forbidden to use read
or any regular grammar. This limitation is imposed by Rgc (see
Regular Parsing) that intrinsicly associate buffers with regular
grammars. If the current Rgc implementation is improved on the coming
version this restriction will be suppressed.
The following exemple is a simple server which waits for a connection
on the port 1234
listening socket with the telnet command. With the given
example, this can be
achived by typing the following command in a window shell:
$ telnet localhost 1234 3. Once the connection with the
distant program is established, we read a line on the input port
associated to the socket and we write the length of this line on its
output port.
(let ((s (make-server-socket 1234)))
(socket-accept-connection s)
(let ((l (read-line (socket-input s))))
(fprint (socket-output s) "Length is: " (string-length l))
(flush-output-port (socket-output s)))
(socket-shutdown s))
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socket-close socket | bigloo procedure |
The function socket-close closes the connection established with
a socket-client .
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socket-shutdown socket [close] | bigloo procedure |
Socket-shutdown shutdowns the connection associated to socket .
Close is a boolean; it indicates if the socket must be closed or not,
when the connection is destroyed. Closing the socket forbids further
connections on the same port with the socket-accept-connection
procedure. Omitting a value for close implies the closing of socket.
The result of socket-shutdown is undefined.
The following example shows a simple server: when there is a new connection
on the port number 1234, the server displays the first line sent to it by the
client, discards the others and go back waiting for further client connections.
(let ((s (make-server-socket 1234)))
(let loop ()
(socket-accept-connection s)
(print "I've read: " (read-line (socket-input s)))
(socket-shutdown s #f)
(loop)))
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socket-down? socket | bigloo procedure |
Returns #t if socket has been previously closed
with socket-shutdown . It returns #f otherwise.
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socket-dup socket | bigloo procedure |
Returns a copy of socket .
note:This function is part of the old Bigloo
API. It was intended to be used in conjunction with
socket-accept-connection . The new API made of socket-accept
and socket-close should be preferred.
The original and the copy socket can be used interchangeably. However,
if a new connection is accepted on one socket, the characters
exchanged on this socket are not visible on the other socket.
Duplicating a socket is useful when a server must accept multiple
simultaneous connections. The following example creates a server
listening on port 1234. This server is duplicated and, once two
clients are present, a message is sent on both connections.
(define s1 (make-server-socket 1234))
(define s2 (socket-dup s1))
(socket-accept-connection s1)
(socket-accept-connection s2)
;; blocks until two clients are present
(display #"Hello,\n" (socket-output s1))
(display #"world\n" (socket-output s2))
(flush-output-port (socket-output s1))
(flush-output-port (socket-output s2))
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Here is another example of making use of sockets:
(define s1 (make-server-socket))
(define s2 #unspecified)
(dynamic-wind
;; Init: Launch an xterm with telnet running
;; on the s listening port and connect
(lambda ()
(run-process "/usr/X11R6/bin/xterm" "-display" ":0" "-e" "telnet" "localhost"
(number->string (socket-port-number s1)))
(set! s2 (socket-accept s1))
(display #"\nWelcome on the socket REPL.\n\n> " (socket-output s2))
(flush-output-port (socket-output s2)))
;; Action: A toplevel like loop
(lambda ()
(let loop ()
(let ((obj (eval (read (socket-input s2)))))
(fprint (socket-output s2) "; Result: " obj)
(display "> " (socket-output s2))
(flush-output-port (socket-output s2))
(loop))))
;; Termination: We go here when
;; -a: an error occurs
;; -b: connection is closed
(lambda ()
(print #"Shutdown ......\n")
(socket-close s2)
(socket-shutdown s1)))
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Here is a second example that uses sockets. It implements
a client-server architecture and it uses unbufferized
(see socket-accept ) input ports.
First, here is the code of the client:
(module client)
(let* ((s (make-client-socket "localhost" 8080 #f))
(p (socket-output s)))
(display "string" p)
(newline p)
(display "abc" p)
(flush-output-port p)
(let loop ()
(loop)))
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Then, here is the code of the server:
(module server)
(let* ((s (make-server-socket 8080))
(s2 (socket-accept s #f)))
(let ((pin (socket-input s2)))
(let loop ()
(display (read-char pin))
(flush-output-port (current-output-port))
(loop))))
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At, to conclude here the source code for a server waiting for multiple
consecutive connections:
(define (main argv)
(let ((n (if (pair? (cdr argv))
(string->integer (cadr argv))
10))
(s (make-server-socket)))
(print "s: " s)
(let loop ((i 0))
(if (<fx i n)
(let ((s2 (socket-accept s)))
(print "i: " i " " s2)
(print (read-line (socket-input s2)))
(socket-close s2)
(loop (+fx i 1)))
(socket-shutdown s)))))
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