Glib/Gio Asynchronous or Threaded UDP Server - c

Question

I have currently a synchronous UDP application receiving messages.
The code :
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <glib.h>
#include <gio/gio.h>
int main(argc,argv)
int argc;
char ** argv;{
char buf[256], *ptr, sep[] = "| ";
GError * error = NULL;
GSocket * socket;
GSocketAddress *gsockAddr, *gfromAddr;
guint16 udp_port = 1500;
//Creates socket udp ipv4
socket = g_socket_new(G_SOCKET_FAMILY_IPV4,
G_SOCKET_TYPE_DATAGRAM,
G_SOCKET_PROTOCOL_UDP,
&error);
g_assert(error == NULL);
if (socket == NULL) {
g_print("ERROR");
exit(1);
}
//sockaddr struct like
gsockAddr = G_SOCKET_ADDRESS(g_inet_socket_address_new(g_inet_address_new_any(G_SOCKET_FAMILY_IPV4), udp_port));
if(gsockAddr == NULL){
g_error("Error socket\n");
exit(1);
}
//
if (g_socket_bind (socket, gsockAddr, TRUE, NULL) == FALSE){
g_print("Error bind\n");
exit(1);
}
int bytes = g_socket_receive_from (socket,
&gfromAddr,
buf,
255,
NULL,
&error);
if (bytes == -1) {
g_warning ("Failed to receive from socket: %s", error->message);
g_error_free (error);
return TRUE;
}
g_message("Server receive: %s", buf);
guint16 port = g_inet_socket_address_get_port(G_INET_SOCKET_ADDRESS(gfromAddr));
g_print("...from %s(%d)\n",g_inet_address_to_string(g_inet_socket_address_get_address(G_INET_SO CKET_ADDRESS(gfromAddr))), (int) port);
exit(0);
}
So, I want to make the receive operation, non-blocking instead of blocking. I want to make it either ansynchronous, or/and threaded so that, meanwhile, I could do other operations related to the application I want to develop.
But I did not suceed to make it like I want. I tried to use GLib IO Channels, but I can not make it works. The processus is waiting, but only because of the Main Loop (I can not telnet the application).
The code :
#include <gio/gio.h>
#include <glib.h>
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#define BLOCK_SIZE 1024
static gboolean
gio_read_socket (GIOChannel *channel,
GIOCondition condition,
gpointer data)
{
char buf[1024];
gsize bytes_read;
GError *error = NULL;
if (condition & G_IO_HUP) return FALSE; /* this channel is done */
g_io_channel_read_chars (channel, buf, sizeof (buf), &bytes_read,
&error);
g_assert (error == NULL);
buf[bytes_read] = '\0';
g_print ("%s", buf);
return TRUE;
}
int
main (int argc, char **argv)
{
GSocket * s_udp;
GError *err = NULL;
guint16 udp_port = 5556;
s_udp = g_socket_new(G_SOCKET_FAMILY_IPV4,
G_SOCKET_TYPE_DATAGRAM,
G_SOCKET_PROTOCOL_UDP,
&err);
g_assert(err == NULL);
if (s_udp == NULL) {
g_print("ERROR");
exit(1);
}
g_socket_bind(s_udp,
G_SOCKET_ADDRESS(g_inet_socket_address_new(g_inet_address_new_any(G_SOCKET_FAMILY_IPV4), udp_port)),
TRUE,
&err);
g_assert(err == NULL);
int fd = g_socket_get_fd(s_udp);
GIOChannel* channel = g_io_channel_unix_new(fd);
guint source = g_io_add_watch(channel, G_IO_IN,
(GIOFunc) gio_read_socket, NULL);
g_io_channel_unref(channel);
GMainLoop *loop = g_main_loop_new(NULL, FALSE);
g_main_loop_run(loop);
g_main_loop_unref(loop);
}
I am quite a beginner with GLib/Gio, and I think I am doing wrong with the IO Channels. I would like to add it to the main loop as an event, so that I could use my callback function. Maybe there is a simpler way to do that.
Besides, I have a TCP asynchronous and threaded server that is working, but I did not find how to do the same with UDP (using a GThreadedSocketService and creating a socket listener, then adding the service to the main loop. Easy as pie with TCP).
Do you have any idea how to proceed ? If you know how to do but only with the basic API socket, I still take it ! Thanks.

Answer 1

I figure it out.
I am indeed quite a beginner. Because, when I wanted to test my udp application (the second code block), I used telnet to connect to it and try to send messages. However, we can not telnet udp applications of course...
So I tried with a simple udp sender (I used Glib/Gio for it by the way) instead of telnet and it worked, perfectly non-blocking and reusable. I did make some changes but basically, it is the same. I put an idle function to show you how non-blocking it is, whether this can help someone one day.
My simple Glib/Gio UDP app, non blocking :
#include <gio/gio.h>
#include <glib.h>
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#define BLOCK_SIZE 1024
static gboolean
gio_read_socket (GIOChannel *channel,
GIOCondition condition,
gpointer data)
{
char buf[1024];
gsize bytes_read;
GError *error = NULL;
if (condition & G_IO_HUP) return FALSE; /* this channel is done */
g_io_channel_read_chars (channel, buf, sizeof (buf), &bytes_read,
&error);
g_assert (error == NULL);
buf[bytes_read] = '\0';
g_print ("%s", buf);
int *a = data;
*a = *a + 1;
return TRUE;
}
gboolean
idleCpt (gpointer user_data){
int *a = user_data;
g_print("%d\n", *a);
sleep(1);
return TRUE;
}
int
main (int argc, char **argv)
{
GSocket * s_udp;
GError *err = NULL;
int idIdle = -1, dataI = 0;
guint16 udp_port = 1505;
GSocketAddress * gsockAddr = G_SOCKET_ADDRESS(g_inet_socket_address_new(g_inet_address_new_any(G_SOCKET_FAMILY_IPV4), udp_port));
s_udp = g_socket_new(G_SOCKET_FAMILY_IPV4,
G_SOCKET_TYPE_DATAGRAM,
G_SOCKET_PROTOCOL_UDP,
&err);
g_assert(err == NULL);
if (s_udp == NULL) {
g_print("ERREUR");
exit(1);
}
if (g_socket_bind (s_udp, gsockAddr, TRUE, NULL) == FALSE){
g_print("Erreur bind\n");
exit(1);
}
g_assert(err == NULL);
int fd = g_socket_get_fd(s_udp);
GIOChannel* channel = g_io_channel_unix_new(fd);
guint source = g_io_add_watch(channel, G_IO_IN,
(GIOFunc) gio_read_socket, &dataI);
g_io_channel_unref(channel);
GMainLoop *loop = g_main_loop_new(NULL, FALSE);
idIdle = g_idle_add(idleCpt, &dataI);
g_main_loop_run(loop);
}
The code is not perfect, there is a lot of optimisations to make, but we can do nice things from that I think. If you want to see my udp sender, just ask.