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FIFO chat
Socket chat
A good exercise to get to know and practice the intricacies of handling communication channels is brewing a chat program. This example shows an example of how to realize such a 'chat' application between two windows. To make the example more exciting (and to learn a little more), I wrote the client application in Python and the server in C (though I used g++ to compile, I didn't use classes).
The main challenge was the requirement that reception be implemented asynchronously - without a wait loop - as the program was just a test for a larger control program.
There's another version available which uses sockets instead of FIFOs.
The diagram left shows the elements used to construct the users
interface:
The green rectangle is the container (GtkVBox) for the entire GUI, while the GtkLabel and GtkButton are located in a GtkHBox (blue rectangle). |
#!/usr/bin/env python
# -*- coding: utf-8 -*-
#
# client.py
#
# Copyright 2014 John Coppens <john@jcoppens.com>
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program 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 General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
# MA 02110-1301, USA.
#
#
import gtk
import pygtk
import sys
import gobject, glib
import os, os.path
FIFO_ROOT = "./fifo"
class Client():
""" The Client class takes care of our communications by FIFO.
"""
def __init__(self, fifo_root):
""" Create the FIFO
"""
self.fifo_root = fifo_root
# First check if the client socket is left over from a previous session
if os.path.exists(self.fifo_root + '.client'):
os.remove(self.fifo_root + '.client')
# Then create a new one
os.mkfifo(self.fifo_root + '.client')
# Then check if the server has created a fifo
if os.path.exists(self.fifo_root + '.server'):
self.out_fd = os.open(self.fifo_root + '.server',
os.O_WRONLY | os.O_APPEND)
self.out_f = os.fdopen(self.out_fd, "w")
print "opening client for read"
self.in_fd = os.open(self.fifo_root + '.client',
os.O_RDONLY | os.O_NONBLOCK, 0o644)
self.in_f = os.fdopen(self.in_fd)
print "client open"
else:
print "Server is not running!"
sys.exit(1)
self.show_status_cb = None
self.show_data_cb = None
glib.io_add_watch(self.in_fd, glib.IO_IN, self.process_input)
def process_input(self, port, cond):
""" This function is called asynchronously when data is received.
"""
msg = self.in_f.readline() # Get the message from the FIFO
self.show_data(msg) # And send it to MainWindow
return True # We want to stay alive
def send(self, msg):
self.out_f.write(msg)
self.out_f.flush()
def show_status(self, msg):
""" Show status changes from this class, either on the terminal,
or else by calling the callback installed by set_status_show().
"""
if self.show_status_cb == None:
print "Status: ", msg
else:
self.show_status_cb(msg)
def show_data(self, msg):
""" Show received messages, either on the terminal,
or else by calling the callback installed by set_data_show().
"""
if self.show_data_cb == None:
print "Data: ", msg
else:
self.show_data_cb(msg)
def set_status_show(self, show_status_cb):
self.show_status_cb = show_status_cb
def set_data_show(self, show_data_cb):
self.show_data_cb = show_data_cb
class MainWindow(gtk.Window):
def __init__(self):
gtk.Window.__init__(self);
self.connect("delete-event", self.destroy);
self.set_size_request(400, 300)
# Make the upper window, which the received text.
txtview = gtk.TextView()
self.txtbff = gtk.TextBuffer()
self.txttagtable = self.txtbff.get_tag_table()
txtview.set_buffer(self.txtbff)
txtview.set_can_focus(False)
texttag_red = gtk.TextTag("red")
texttag_red.set_property("foreground", "red")
self.txttagtable.add(texttag_red)
texttag_black = gtk.TextTag("black")
texttag_black.set_property("foreground", "black")
self.txttagtable.add(texttag_black)
# This is where the text to be transmitted is typed.
# Pressing the 'Enter' key transmits the string.
entry = gtk.Entry()
entry.connect("activate", self.entry_activated);
# And the button to exit the chat program
button = gtk.Button("Quit")
button.set_border_width(4)
button.set_can_focus(False)
button.connect("clicked", self.quit_clicked)
# Left of the button is a label, which can be used to
# show status messages.
hbox = gtk.HBox()
self.statlbl = gtk.Label("")
hbox.pack_start(self.statlbl, expand = True, fill = True)
hbox.pack_start(button, expand = False)
# Pack everything into a VBox, then that into the window.
vbox = gtk.VBox()
vbox.set_spacing(4)
vbox.pack_start(txtview)
vbox.pack_start(entry, expand = False)
vbox.pack_start(hbox, expand = False)
self.add(vbox)
entry.grab_focus()
self.show_all()
def destroy(self, window, data):
""" Called when the MainWindow is closed - this stops the
GTK+ main loop, and terminates the program
"""
gtk.main_quit()
def entry_activated(self, widget):
msg = widget.get_text() + "\n"
self.client.send(msg)
self.show_data(msg, color = 'black')
widget.set_text("")
def show_status(self, msg):
self.statlbl.set_text(msg)
def show_data(self, msg, color = 'red'):
self.txtbff.insert_with_tags_by_name(self.txtbff.get_end_iter(), msg, color)
def set_client(self, client):
""" The client is the communication system which wants to show
things here, and get strings to transmit from the GtkEntry
"""
self.client = client
# We connect callbacks to get news from the client
client.set_status_show(self.show_status)
client.set_data_show(self.show_data)
def quit_clicked(self, widget):
gtk.main_quit()
def run(self):
gtk.main()
def main():
main = MainWindow() # Prepare the main window,
client = Client(FIFO_ROOT) # and the communications package
main.set_client(client) # Announce the client to the main window
main.run()
return 0
if __name__ == '__main__':
main()
/* -*- Mode: C; indent-tabs-mode: t; c-basic-offset: 8; tab-width: 8 -*- */
/*
* main.cc
* Copyright (C) 2014 John Coppens <john@jcoppens.com>
*
* socket_test is free software: you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by the
* Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* socket_test 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include <gtk/gtk.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <string.h>
#include "config.h"
#include "fifocom.h"
#ifdef ENABLE_NLS
# include <libintl.h>
#endif
// For testing propose use the local (not installed) ui file
// #define UI_FILE PACKAGE_DATA_DIR"/ui/socket_test.ui"
#define UI_FILE "src/socket_test.ui"
#define FIFO_ROOT "fifo"
GtkWidget *MainWindow;
GtkTextBuffer *txtbuffer;
// Note: For some strange reason the 'extern "C"' is necessary to define
// handlers for the gtk_builder_connect_signals() call - and only if
// g++ is used!
extern "C" gboolean
quit_button_clicked_cb(GtkButton *btn)
{
gtk_main_quit();
}
extern "C" void
on_main_window_delete_event(GtkWidget *w)
{
gtk_main_quit();
}
extern "C" void
tx_entry_activate(GtkEntry *entry)
{
write_chars(channel, (char *) gtk_entry_get_text(entry));
write_chars(channel, (char *) "\n");
gtk_entry_set_text(entry, "");
}
void
add_to_textbuffer(char *message)
{
GtkTextIter iter;
gtk_text_buffer_get_end_iter(txtbuffer, &iter);
gtk_text_buffer_insert(txtbuffer, &iter, message, strlen(message));
}
int
main (int argc, char *argv[])
{
GtkWidget *txtview;
GError *error = NULL;
int listenfd;
gtk_init(&argc, &argv);
GtkBuilder *builder = gtk_builder_new();
gtk_builder_add_from_file(builder, UI_FILE, &error);
gtk_builder_connect_signals(builder, NULL);
// Get references to some of the widgets we use frequently
MainWindow = GTK_WIDGET(gtk_builder_get_object(builder, "main_window"));
txtview = GTK_WIDGET(gtk_builder_get_object(builder, "textview1"));
MainWindow = GTK_WIDGET(gtk_builder_get_object(builder, "tx_entry"));
// 'Manually' create a textbuffer and connect it to the textview
txtbuffer = gtk_text_buffer_new(NULL);
gtk_text_view_set_buffer(GTK_TEXT_VIEW(txtview), txtbuffer);
g_object_unref(G_OBJECT(builder)); // Don't need the builder anymore
gtk_widget_show_all(MainWindow); // Queue drawing all widgets
start_comm(FIFO_ROOT, add_to_textbuffer);
gtk_main();
close_comm();
return 0;
}
/* -*- Mode: C; indent-tabs-mode: t; c-basic-offset: 8; tab-width: 8 -*- */
/*
* socketcom.h
* Copyright (C) 2014 Unknown <root@on6jc>
*
* socket_test is free software: you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by the
* Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* socket_test 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#ifndef _SOCKETCOM_H_
#define _SOCKETCOM_H_
typedef void (*read_callback)(char *);
#include <gtk/gtk.h>
extern GIOChannel *channel;
gboolean read_watch(GIOChannel *source, GIOCondition cond, gpointer data);
gboolean write_chars(GIOChannel *dest, char *message);
void start_comm(const char *fifo_root, read_callback callback);
void close_comm();
#endif // _SOCKETCOM_H_
/* -*- Mode: C; indent-tabs-mode: t; c-basic-offset: 8; tab-width: 8 -*- */
/*
* socketcom.cc
* Copyright (C) 2014 Unknown <root@on6jc>
*
* socket_test is free software: you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by the
* Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* socket_test 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <glib.h>
#include "fifocom.h"
GIOChannel *channel;
char *client_fn, *server_fn;
gboolean
read_watch(GIOChannel *source, GIOCondition cond, gpointer data)
{
char bff[100];
GError *error = NULL;
gsize bytes_read;
GIOStatus ret;
printf("read_watch called\n");
ret = g_io_channel_read_chars(source, bff, sizeof(bff), &bytes_read, &error);
if (ret == G_IO_STATUS_ERROR)
g_error("Error reading: %s\n", error->message);
else {
bff[bytes_read] = 0;
((read_callback) data)(bff);
printf("Got: %s\n", bff);
}
return TRUE;
}
gboolean
write_chars(GIOChannel *dest, char *message)
{
int out_fd;
printf("Trying to write %s\n", message);
out_fd = open(client_fn, O_WRONLY);
write(out_fd, message, strlen(message));
close(out_fd);
return TRUE;
}
void
start_comm(const char *fifo_root, read_callback callback)
{
int in_fd, ch_id;
server_fn = g_strdup_printf("%s.server", fifo_root);
client_fn = g_strdup_printf("%s.client", fifo_root);
if (g_file_test(server_fn, G_FILE_TEST_EXISTS))
unlink(server_fn); // g_remove wasn't declared???
// Then create a new one
mkfifo(server_fn, 0666);
// Open the file for reading
in_fd = open(server_fn, O_RDONLY | O_NONBLOCK);
channel = g_io_channel_unix_new(in_fd);
ch_id = g_io_add_watch(channel, G_IO_IN, (GIOFunc) read_watch,
(gpointer) callback);
printf("IOchannel ID: %d\n", ch_id);
}
void
close_comm()
{
GError *error = NULL;
g_io_channel_shutdown(channel, TRUE, &error);
}
And to those at Pygments for the syntax coloring program.
Anjuta was used to write and test the C code, and Geany to edit the Python code.
7769(c) John Coppens ON6JC/LW3HAZ |