UDP Server-Client

[DGvMDjzh]

This is a simple server-client code. The client sends the first packet, server receives it along with the client's address and sends a response. The code works perfectly when SERVER_IP is set to "127.0.0.1", but every-time I try this over the internet the client never receives a response from the server.

What am I doing wrong?

//Server
bool Server() {
 WSADATA WSA;
 SOCKET Socket;
 SOCKADDR_IN LocalAddr;

 if (WSAStartup(0x0202,&WSA)) return false;
 if (WSA.wVersion != 0x0202) return false;

 Socket = socket(AF_INET,SOCK_DGRAM,IPPROTO_UDP);

 LocalAddr.sin_family = AF_INET;
 LocalAddr.sin_port = htons(7777);
 LocalAddr.sin_addr.s_addr = INADDR_ANY;

 if (bind(Socket,(SOCKADDR*)&LocalAddr,sizeof(SOCKADDR))) return false;

 SOCKADDR_IN ClientAddr;
 int i = sizeof(SOCKADDR);
 char data[256];

// recieve first packet and get client address
 if (recvfrom(Socket,data,256,0,(SOCKADDR*)&ClientAddr,&i) <= 0) return false;

// send response
 if (sendto(Socket,data,256,0,(SOCKADDR*)&ClientAddr,sizeof(SOCKADDR_IN)) > 0) printf("Sent!");

 return true;
}

#define SERVER_IP "127.0.0.1"

//Client
bool Client() {
 WSADATA WSA;
 SOCKET Socket;
 SOCKADDR_IN ServerAddr;

 if (WSAStartup(0x0202,&WSA)) return false;
 if (WSA.wVersion != 0x0202) return false;

 Socket = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
 if (Socket == INVALID_SOCKET) return false;

 ServerAddr.sin_family = AF_INET;
 ServerAddr.sin_port = htons(7777);
 ServerAddr.sin_addr.s_addr = inet_addr(SERVER_IP);

 char data[256];

//send first packet
 if (sendto(Socket,data,256,0,(SOCKADDR*)&ServerAddr,sizeof(SOCKADDR_IN)) <= 0) return false;

//recieve response
 if (recvfrom(Socket,data,256,0,NULL,NULL) > 0) printf("Recieved!");

 return true;
}

[coder777]

but every-time I try this over the internet

What exactly does that mean? Where is the server program running?

[DGvMDjzh]

Both the server and client are running on the same machine.
When the client sends the packet to the public IP address it does it successfully, but never receives a response from the server.

[coder777]

I don't know what this 'public IP address' is.


Usually the communication with the internet works (roughly) as follows:

Your computer sends a request to the modem. The modem sends this request to the server in the internet. And the response backwards.

In other words (usually): your computer doesn't have a public ip adress visible in the internet. Your modem (which is usually also a router) has.

[DGvMDjzh]

Firewall issue, solved.