Thread: access violation when connecting to server

Hey folks!

Here's the compilable code. The line in red is what causes the access violation.

Code:

#include <winsock2.h>
#include <ws2tcpip.h>
#include <stdio.h>
#include <stdlib.h>

#define STORAGE_LEN 1000
#define DEFAULT_PORT "80"

char storage[STORAGE_LEN];
SOCKET ConnectSocket = INVALID_SOCKET;

void write_to_file(char *storage)
{
	FILE *p_openfile = fopen("c:\\programs\\networking\\webpagecontent.txt" , "a+");
	fprintf(p_openfile, "%s\n", storage);
	fclose(p_openfile);
}

int main(int argc, char **argv)
{
	WSADATA wsaData;
	int iResult;
	struct addrinfo *result = NULL,
				*ptr = NULL,
				hints;

        // Validate parameters
        if(argc !=2) {
		printf("usage: %s server-name\n", argv[0]);
		return 1;
	}

	// Initialize Winsock
	iResult = WSAStartup(MAKEWORD(2,2), &wsaData);
	if(iResult != 0) {
		printf("WSAStartup failed: %d\n", iResult);
		return 1;
	}

	sprintf(storage, "WSAStartup = %d\n", iResult);
	write_to_file(storage);

	ZeroMemory(&hints, sizeof(hints));
	hints.ai_family = AF_UNSPEC;
	hints.ai_socktype = SOCK_STREAM;
	hints.ai_protocol = IPPROTO_TCP;

	// Resolve the server address and port
	iResult = getaddrinfo(argv[1], DEFAULT_PORT, &hints, &result);
	if(iResult != 0) {
		printf("getaddrinfo failed: %d\n", iResult);
		WSACleanup();
		return 1;
	}

	sprintf(storage, "getaddrinfo = %d\n", iResult);
	write_to_file(storage);

	// Attempt to connect to an address until one succeeds
	for(ptr = result; ptr != NULL; ptr = ptr->ai_next) {
		
		// Create a socket for connecting to the server
		ConnectSocket = socket(ptr->ai_family, ptr->ai_socktype, ptr->ai_protocol);
		if(ConnectSocket == INVALID_SOCKET) {
			printf("Error at socket(): %ld\n", WSAGetLastError());
			freeaddrinfo(result);
			WSACleanup();
			return 1;
		}
	}

	sprintf(storage, "socket = %d\n", ConnectSocket);
	write_to_file(storage);

	// Connect to server
	iResult = connect(ConnectSocket, ptr->ai_addr, (int)ptr->ai_addrlen);
	if(iResult == SOCKET_ERROR) {
		closesocket(ConnectSocket);
		ConnectSocket = INVALID_SOCKET;
	}

	freeaddrinfo(result);

	if(ConnectSocket == INVALID_SOCKET) {
		printf("Unable to connect to the server!\n");
		return 1;
	}

	return 0;
}

I am still a bit too newbie to know what is the exact problem. Is it because ptr is NULL? Am I supposed to create another struct addrinfo object, and assign ptr to it?

If I was to write

Code:

ptr = result;

before the line in red, a SOCKET ERROR is the result.

Thanks in advance.

Oh, found the problem, I should have closed the for() loop in blue after the connection was made to the server, because ptr is still needed.