Issue with retrieving client IP address on a winsock 2 based server program - sockets

Question

Hello I made this program based on the msdn winsock2.h tutorial.I have server program and a client one.Everything works fine, I even made one sided chat from the server to the client, more like broadcast.Now i want to see the client's IP address when he connects.I think i did it right but, on every connect it shows different address in strange form like 12.2.90.0 then, 12.2.46.0.
This is the server code :
#include <cstdlib>
#include <iostream>
#include <winsock2.h>
#include <ws2tcpip.h>
#include <stdio.h>
#include <iphlpapi.h>
#define DEFAULT_PORT "27015"
using namespace std;
int main(int argc, char *argv[])
{
WSADATA wsaData;
int iResult;
SOCKET ListenSocket = INVALID_SOCKET;
SOCKET ClientSocket = INVALID_SOCKET;
struct sockaddr_in client_info;
char * addr;
struct addrinfo *result = NULL;
struct addrinfo hints;
int iSendResult;
char buffer[50];
char typebuffer[50];
char connected_ip[15]= "\0";
int port;
// Initialize Winsock
iResult = WSAStartup(MAKEWORD(2,2), &wsaData);
if (iResult != 0) {
printf("WSAStartup failed with error: %d\n", iResult);
return 1;
} cout<<"Winsock initialized..."<<endl;
ZeroMemory(&hints, sizeof(hints));
hints.ai_family = AF_INET;
hints.ai_socktype = SOCK_STREAM;
hints.ai_protocol = IPPROTO_TCP;
hints.ai_flags = AI_PASSIVE;
// Resolve the server address and port
iResult = getaddrinfo(NULL, DEFAULT_PORT, &hints, &result);
if ( iResult != 0 ) {
printf("getaddrinfo failed with error: %d\n", iResult);
WSACleanup();
return 1;
}
// Create a SOCKET for connecting to server
ListenSocket = socket(result->ai_family, result->ai_socktype, result->ai_protocol);
if (ListenSocket == INVALID_SOCKET) {
printf("socket failed with error: %ld\n", WSAGetLastError());
freeaddrinfo(result);
WSACleanup();
return 1;
}
// Setup the TCP listening socket
iResult = bind( ListenSocket, result->ai_addr, (int)result->ai_addrlen);
if (iResult == SOCKET_ERROR) {
printf("bind failed with error: %d\n", WSAGetLastError());
freeaddrinfo(result);
closesocket(ListenSocket);
WSACleanup();
return 1;
} else cout<<"Listening socket initialized...\nAccepting connections now..."<<endl;
freeaddrinfo(result);
iResult = listen(ListenSocket, SOMAXCONN);
if (iResult == SOCKET_ERROR) {
printf("listen failed with error: %d\n", WSAGetLastError());
closesocket(ListenSocket);
WSACleanup();
return 1;
}
// Accept a client socket
ClientSocket = accept(ListenSocket, (struct sockaddr*)&client_info, NULL);
if (ClientSocket == INVALID_SOCKET) {
printf("accept failed with error: %d\n", WSAGetLastError());
closesocket(ListenSocket);
WSACleanup();
return 1;
} else
// converting the address in readable form
addr = inet_ntoa(client_info.sin_addr);
printf("Client connected, IP address is: %s\n", addr );
{
}
closesocket(ListenSocket);
for(;;)
{
cin.getline(typebuffer,50);
strcpy(buffer,"SERVER: ");
strcat(buffer,typebuffer);
send( ClientSocket, buffer, 50, 0 );
*buffer = '\0';
}
system("PAUSE");
return EXIT_SUCCESS;
}

Answer 1

You are providing a sockaddr_in struct to accept(), but you are not telling it how large the struct is. You are not zeroing out the sockaddr_in, and accept() is not filling it in, so you end up with random results when calling inet_ntoa(). This behavior is documented:
accept function
If addr and/or addrlen are equal to NULL, then no information about the remote address of the accepted socket is returned.
The addrlen parameter cannot be NULL if the addr parameter is not NULL:
int addrlen = sizeof(client_info); // <-- Add this
ClientSocket = accept(ListenSocket, (struct sockaddr*)&client_info, &addrlen);