Why can't my client connect to the server? - c++

Question

I try to make a application that client send a message and the server respond on the same machine using winsock TCP c++. The problem is that after the server waited for client to connect, I ran the client code and it stopped at the connect and exit. This is my code.
Server:
#include <stdio.h>
#include <tchar.h>
#include <winsock2.h>
#include <iostream>
#define MY_PORT 8888
using namespace std;
int _tmain(int argc, _TCHAR* argv[])
{
//Init Winsock
WSADATA SData;
if (WSAStartup(0x0202, &SData) != 0)
{
cout << "KHONG THE KHOI DONG WINSOCK";
return 1;
}
//Init Socket
int listeningSocket;
if ((listeningSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP)) < 0)
{
perror("socket failed");
WSACleanup();
exit(EXIT_FAILURE);
}
//Set IP and PORT
sockaddr_in server_addr;
server_addr.sin_family = AF_INET;
server_addr.sin_port = htons(MY_PORT);
server_addr.sin_addr.s_addr = INADDR_ANY;
//Bind
if (bind(listeningSocket, (struct sockaddr *)&server_addr, sizeof(server_addr)) < 0)
{
perror("bind failed");
closesocket(listeningSocket);
WSACleanup();
exit(EXIT_FAILURE);
}
//Listen
if (listen(listeningSocket, 5) < 0)
{
perror("listen failed");
closesocket(listeningSocket);
WSACleanup();
exit(EXIT_FAILURE);
}
//Accept
int new_socket;
sockaddr_in client_addr;
int nSizeAddr = sizeof(sockaddr);
if (new_socket = accept(listeningSocket, (struct sockaddr *)&client_addr, &nSizeAddr) < 0)
{
perror("accept failed");
closesocket(listeningSocket);
WSACleanup();
exit(EXIT_FAILURE);
}
while (1)
{
//recv
char buff[100];
if (recv(new_socket, buff, 100, 0) < 0)
{
perror("recv failed");
closesocket(listeningSocket);
WSACleanup();
exit(EXIT_FAILURE);
}
cout << buff << endl;
//send
string sndStr = "Da nhan";
if (send(new_socket, sndStr.c_str(), sndStr.size(), 0) < 0)
{
perror("send failed");
closesocket(listeningSocket);
WSACleanup();
exit(EXIT_FAILURE);
}
}
//close socket
closesocket(new_socket);
//Cleanup winsock
WSACleanup();
return 0;
}
Client:
#include <stdio.h>
#include <tchar.h>
#include <winsock2.h>
#include <iostream>
#include <string>
#define MY_PORT 8888
using namespace std;
int _tmain(int argc, _TCHAR* argv[])
{
//Init winsock
WSADATA SData;
if (WSAStartup(0x0202, &SData) != 0)
{
cout << "KHONG THE KHOI DONG WINSOCK";
return 1;
}
//Init socket
int clientSocket;
if (clientSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP) < 0)
{
perror("socket failed");
WSACleanup();
exit(EXIT_FAILURE);
}
//Set IP and PORT
sockaddr_in server_addr;
server_addr.sin_family = AF_INET;
server_addr.sin_port = htons(MY_PORT);
server_addr.sin_addr.s_addr = INADDR_ANY; //Vi Client-Server chung 1 may
//Connect
if (connect(clientSocket, (SOCKADDR*)&server_addr, sizeof(server_addr)) < 0)
{
perror("connect failed");
closesocket(clientSocket);
WSACleanup();
exit(EXIT_FAILURE);
}
while (1)
{
//Send
string sndStr;
getline(cin, sndStr);
if (send(clientSocket, sndStr.c_str(), sndStr.size(), 0) < 0)
{
perror("send failed");
closesocket(clientSocket);
WSACleanup();
exit(EXIT_FAILURE);
}
//Recv
char buff[100];
if (recv(clientSocket, buff, 100, 0) < 0)
{
perror("recv failed");
closesocket(clientSocket);
WSACleanup();
exit(EXIT_FAILURE);
}
cout << buff << endl;
}
//Close socket
closesocket(clientSocket);
//Cleanup Winsock
WSACleanup();
}
It had an error at the accept step but I don't know what was the error name. How can I fix it?
The client_socket value turn out INVALID_SOCKET.

Answer 1

EDIT: New problem found - I still don't believe that using INADDR_ANY as a client address is good, but that isn't actually the problem here.
Instead the problem is in the line:
if (clientSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP) < 0)
Note that < has higher precedence than =, so you assign a boolean value to clientSocket here. The similar line in the server code has parenthesis added that makes it work correctly.
Working line in the server code:
if ((listeningSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP)) < 0)
OLD ANSWER: I still stand by this, but it isn't the problem here
.
This is your problem right here (in the client):
server_addr.sin_addr.s_addr = INADDR_ANY; //Vi Client-Server chung 1 may
The way sockets work, is that you create a server socket that listens for incoming connections, and on creation you tell it who to accept connections from. Either from a specific address, a range of addresses, or just from anybody. The third option is the most common one here, and the one you have chosen in your server (bind to address INADDR_ANY).
This part is good.
However, when the client has to connect to the server, you cannot just say: "Connect to whatever!" and expect it to find your server (or anything at all). So when you try to connect with the client socket you have to give it the actual address of the server.
I found a example of how to do this:
serv_addr.sin_family = AF_INET;
serv_addr.sin_port = htons(PORT);
// Convert IPv4 and IPv6 addresses from text to binary form
if (inet_pton(AF_INET, "127.0.0.1", &serv_addr.sin_addr) <= 0)
{
printf("\nInvalid address/ Address not supported \n");
return -1;
}
if (connect(sock, (struct sockaddr*) & serv_addr, sizeof(serv_addr)) < 0)
Change the address to the correct one for your server, if localhost (127.0.0.1) don't work for you.