Function Timeout not working as expected - c++

Question

I'm just starting to learn the C++ and I would like to test what I'm learning on a Raspberry. My project, for now, consist to transfert data from a Raspberry to another through WiFi. This works very well but the problem comes when the Raspberry client disconnects from WiFi. At this time, the Server wait indefinitely. So to avoid that, I search on Google to have a Timeout function and here it is:
class Timeout;
static Timeout * global_timeout_instance = 0;
class Timeout {
public:
int m_timeout;
jmp_buf env;
Timeout(int timeout) : m_timeout(timeout) {
if (global_timeout_instance) {
throw "Timeout already in use";
}
global_timeout_instance = this;
}
~Timeout() {
stop();
global_timeout_instance = 0;
}
static void alarm_handler(int signum) {
longjmp(global_timeout_instance->env, 1);
}
void start() {
Timeout * ptr = this;
if (setjmp(env) != 0) {
// Don't do anything except throw here, since the state
// is... funky...
printf("Alarm fired: %p\n", ptr);
throw global_timeout_instance;
}
signal(SIGALRM, alarm_handler);
alarm(2);
}
void stop() {
alarm(0);
}
};
So this function works very well because when the connection is lost, the program stop directly. But I would like to do some action after the loss of connection. So here is my entire code:
#include <exception>
#include <stdio.h>
#include <string.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <string>
#include <iostream>
#include <cstdio>
#include <setjmp.h>
#include <signal.h>
class Timeout;
static Timeout * global_timeout_instance = 0;
class Timeout {
public:
int m_timeout;
jmp_buf env;
Timeout(int timeout) : m_timeout(timeout) {
if (global_timeout_instance) {
throw "Timeout already in use";
}
global_timeout_instance = this;
}
~Timeout() {
stop();
global_timeout_instance = 0;
}
static void alarm_handler(int signum) {
longjmp(global_timeout_instance->env, 1);
}
void start() {
Timeout * ptr = this;
if (setjmp(env) != 0) {
// Don't do anything except throw here, since the state
// is... funky...
printf("Alarm fired: %p\n", ptr);
throw global_timeout_instance;
}
signal(SIGALRM, alarm_handler);
alarm(2);
}
void stop() {
alarm(0);
}
};
int main(int argc , char *argv[])
{
int socket_desc , client_sock , c , read_size;
struct sockaddr_in server , client;
char client_message[2000];
//Create socket
socket_desc = socket(AF_INET , SOCK_STREAM , 0);
if (socket_desc == -1)
{
printf("Could not create socket");
}
puts("Socket created");
//Prepare the sockaddr_in structure
server.sin_family = AF_INET;
server.sin_addr.s_addr = INADDR_ANY;
server.sin_port = htons( 8888 );
//Bind
if( bind(socket_desc,(struct sockaddr *)&server , sizeof(server)) < 0)
{
//print the error message
perror("bind failed. Error");
return 1;
}
puts("bind done");
//Listen
listen(socket_desc , 3);
//Accept and incoming connection
puts("Waiting for incoming connections...");
c = sizeof(struct sockaddr_in);
//accept connection from an incoming client
client_sock = accept(socket_desc, (struct sockaddr *)&client, (socklen_t*)&c);
if (client_sock < 0)
{
perror("accept failed");
return 1;
}
puts("Connection accepted");
//Receive a message from client
while(1)
{
try
{
Timeout timeout(1);
timeout.start();
read_size = recv(client_sock , client_message , 2000 , MSG_WAITALL);
}
catch(Timeout * t)
{
printf("Timeout detected\n");
// Do some action later
}
printf("%d\n", read_size);
if(client_message !="")
{
puts(client_message);
}
else
{
printf("Not Ok");
}
memset(client_message, 0, sizeof(client_message));
}
if(read_size == 0)
{
puts("Client disconnected");
fflush(stdout);
}
else if(read_size == -1)
{
perror("recv failed");
}
return 0;
}
I don't know how I can do some action after the Timeout.
Here is the message I received when the program stop:
Alarm fired: 0x7eff8c40 terminate called after throwing an instance of
'Timeout*' Aborted
Can someone help me on this problem?
Thank you.
Kevin