I'm a newbie in Network Programming, started to learn how to use WinSock in C.
I don't have any knowledge in Networking right now.
Anyway, I've written the following code for Client and Server, using WinSock.
Server:
#include <stdio.h>
#include <stdlib.h>
#include <winsock2.h>
#include <ws2tcpip.h>
#define MY_ERROR 1
#define PORT 7777
#define MAX_NUM_CLIENTS 1 /* I don't know how to thread right now. */
#define MAX_CLIENT_MSG_LEN 1000
int main()
{
WSADATA wsa;
SOCKET mySocket, acceptSocket;
struct sockaddr_in server, client;
int sockAddrInLength = sizeof(struct sockaddr_in);
char clientMessage[MAX_CLIENT_MSG_LEN];
int clientMessageLength;
char* message;
int running = 1;
if(WSAStartup(MAKEWORD(2,2), &wsa) != 0)
{
fprintf(stderr, "WSAStartup failed.\n");
return MY_ERROR;
}
printf("WSAStartup succeded.\n");
mySocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
if (mySocket == INVALID_SOCKET)
{
fprintf(stderr, "Socket creation failed.\n");
return MY_ERROR;
}
printf("Socket creation succeeded.\n");
server.sin_addr.s_addr = INADDR_ANY;
server.sin_family = AF_INET;
server.sin_port = htons(PORT);
if (bind(mySocket, (struct sockaddr*) &server, sizeof server) == SOCKET_ERROR)
{
fprintf(stderr, "Binding socket on port %d failed.\n", PORT);
return MY_ERROR;
}
printf("Binding socket on port %d successfully.\n", PORT);
while (running)
{
listen(mySocket, MAX_NUM_CLIENTS);
printf("Waiting for a connection...\n");
acceptSocket = accept(mySocket, (struct sockaddr*) &client, &sockAddrInLength);
if (acceptSocket == INVALID_SOCKET)
{
fprintf(stderr, "Accept failed.\n");
return MY_ERROR;
}
printf("Accept succeeded.\n");
if ((clientMessageLength = recv(acceptSocket, clientMessage, sizeof clientMessage, 0)) == SOCKET_ERROR)
{
fprintf(stderr, "Recv failed.\n");
return MY_ERROR;
}
printf("Recv succeeded.\n");
printf("Data:\n");
clientMessage[clientMessageLength] = NULL; /* Null terminator */
printf("Client: %s\n", clientMessage);
message = "Hello client, I'm the server. Bye bye. :-)\n";
if (send(acceptSocket, message, strlen(message), 0) < 0)
{
fprintf(stderr, "Send failed.\n");
return MY_ERROR;
}
printf("Send succeded.\n");
}
closesocket(mySocket);
WSACleanup();
getchar();
return 0;
}
And this is the code for the Client:
#include <stdio.h>
#include <stdlib.h>
#include <winsock2.h>
#include <ws2tcpip.h>
#define IP /* My IP */
#define MY_ERROR 1
#define PORT 7777
#define MAX_SERVER_MSG_LEN 1000
int main()
{
WSADATA wsa;
SOCKET mySocket;
struct sockaddr_in server;
char* message;
char serverMessage[MAX_SERVER_MSG_LEN];
int serverMessageLength;
if(WSAStartup(MAKEWORD(2,2), &wsa) != 0)
{
fprintf(stderr, "WSAStartup failed.\n");
getchar();
return MY_ERROR;
}
printf("WSASucceeded.\n");
mySocket = socket(AF_INET,SOCK_STREAM, IPPROTO_TCP);
if (mySocket == INVALID_SOCKET)
{
fprintf(stderr, "Socket creation failed.\n");
getchar();
return MY_ERROR;
}
server.sin_addr.s_addr = inet_addr(IP);
server.sin_family = AF_INET;
server.sin_port = htons(PORT);
if (connect(mySocket, (struct sockaddr*) &server, sizeof server) < 0)
{
fprintf(stderr, "Connection failed. error: %s\n",WSAGetLastError());
getchar();
return MY_ERROR;
}
printf("Connection established.\n");
message = "Hello server, I'm the sweet client. :-)\n";
if (send(mySocket, message, strlen(message), 0) < 0)
{
fprintf(stderr, "Sending failed.\n");
return MY_ERROR;
}
printf("Sending succeeded.\n");
if ((serverMessageLength = recv(mySocket, serverMessage, sizeof serverMessage, 0)) == SOCKET_ERROR)
{
fprintf(stderr, "Recv failed.\n");
return MY_ERROR;
}
printf("Recv succeeded.\n");
printf("Data:\n");
serverMessage[serverMessageLength] = NULL;
printf("Server: %s", serverMessage);
closesocket(mySocket);
getchar();
return 0;
}
Ok.
When I run both server and client on my comupter, and define IP (in the client code) to be my internal IP (I think, becuase it is the form of 192.168.x.x) it works fine.
When I define IP to be my external IP, it doesn't work on my computer (when I run both program in my computer). The connection failes.
In addition -
When I'm trying to run the client on any other computer, it doesn't work (when IP is defined to be my internal or my external IP), the connection failes.
My questions are:
Why when I run both server & client on my computer, it works just with my internal IP?
What should I do in order that the client could be run on another computer and it will work?
I know that maybe the answer contains terms like "internal/external IPs", "routers", maybe "firewall" or "port forwarding".
Just remember I'm really a newbie in Networking and I don't have any knowledge about those terms, so please: I hope your explnations will be beginner-friendly.
I want to start learning Networking, but my first step is to understand how to use Sockets, and I have a problem in the connetction with other computers.
If you have any articles/something like that in order to give me a better understanding of the problem, it could help too.
Thank you very much! :)