Check if host is alive!

[pobri19]

Hi, I'm trying to write a function to check if a host is alive in a given specific time frame. For example, say I wanted to give this function 5 seconds to check if the host is alive, if a connection cannot be established properly within 5 seconds then I presume the host is down and return 1, otherwise I return 0.

For some reason this function ALWAYS returns 0 even if the host is not alive (aka it thinks the host is alive for some reason...) and the variable 'ret' is always equal to 1.

I'm trying to use a non-blocking socket, then a call to connect and then a call to select with that specific time limit to check if the host is up. I cannot seem to get it working.

// checks whether host is alive with a non-blocking socket and call to select on minimal timeout
int Host_Alive(arguments * args) {
	args->serv.sin_addr.S_un.S_addr = inet_addr(args->sz_address);
	args->serv.sin_family = AF_INET;
	args->serv.sin_port = htons(args->port);

	args->sockfd = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);

	args->sz_address = new char[16];
	strcpy(args->sz_address, inet_ntoa((in_addr)args->serv.sin_addr));

	unsigned long iMode = 0;
	ioctlsocket(args->sockfd, FIONBIO, &iMode); // put socket in non-blocking state

	connect(args->sockfd, (const sockaddr *)&args->serv, sizeof(args->serv));
	
	fd_set socket_set;
	timeval timer;

	socket_set.fd_array[0] = args->sockfd;
	socket_set.fd_count = 1;

	timer.tv_sec = args->timeout;
	
	int ret = select(0, &socket_set, &socket_set, &socket_set, &timer);
	
	if (!ret || ret == SOCKET_ERROR) {
		printf(" [!] Host %s:%d not alive: %d!\n", args->sz_address, args->port, ret);
		free(args);
		closesocket(args->sockfd);
		return 0;
	}

	else
		printf(" [!] Host up: %d!\n", ret);
	
	free(args);
	closesocket(args->sockfd);

	return 1;
}

Thanks!

[xander_tan]

I'm trying to use a non-blocking socket, then a call to connect and then a call to select with that specific time limit to check if the host is up. I cannot seem to get it working.

// checks whether host is alive with a non-blocking socket and call to select on minimal timeout
int Host_Alive(arguments * args) {
	args->serv.sin_addr.S_un.S_addr = inet_addr(args->sz_address);
	args->serv.sin_family = AF_INET;
	args->serv.sin_port = htons(args->port);

	args->sockfd = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);

	args->sz_address = new char[16];
	strcpy(args->sz_address, inet_ntoa((in_addr)args->serv.sin_addr));

	unsigned long iMode = 0;
	ioctlsocket(args->sockfd, FIONBIO, &iMode); // put socket in non-blocking state

	connect(args->sockfd, (const sockaddr *)&args->serv, sizeof(args->serv));
	
	fd_set socket_set;
	timeval timer;

	socket_set.fd_array[0] = args->sockfd;
	socket_set.fd_count = 1;

	timer.tv_sec = args->timeout;
	
	int ret = select(0, &socket_set, &socket_set, &socket_set, &timer);
	
	if (!ret || ret == SOCKET_ERROR) {
		printf(" [!] Host %s:%d not alive: %d!\n", args->sz_address, args->port, ret);
		free(args);
		closesocket(args->sockfd);
		return 0;
	}

	else
		printf(" [!] Host up: %d!\n", ret);
	
	free(args);
	closesocket(args->sockfd);

	return 1;
}

Hi there, could you try to get the WSAGetLastError value? It will help, you may want to look into this: http://msdn.microsoft.com/en-us/libr...41(VS.85).aspx