How to get the ip address in qt/linux?

Question

I am working on a server client project on Qt. The server is running in a machine with more than one network interface. The design is such that the client will discover the server automatically. ie the client will broadcast its IP to a network the server get that message and sends back the server's IP. The problem now is that when I try to get the IP in the server, There are more than 1 IP. How to get the IP of the interface through which server have received the message?

Answer 1

This might be a solution for you

IPAddress FindLocalIPAddressOfIncomingPacket( senderAddr )
{
    foreach( adapter in EnumAllNetworkAdapters() )
    {
        adapterSubnet = adapter.subnetmask & adapter.ipaddress;
        senderSubnet = adapter.subnetmask & senderAddr;
        if( adapterSubnet == senderSubnet )
        {
            return adapter.ipaddress;
        }
    }
}

How to get your own (local) IP-Address from an udp-socket (C/C++)

---

In order to get the incoming peer IP address you can use following solution in C

socklen_t len;
struct sockaddr_storage addr;
char ipstr[INET6_ADDRSTRLEN];
int port;

len = sizeof addr;
getpeername(s, (struct sockaddr*)&addr, &len);

// deal with both IPv4 and IPv6:
if (addr.ss_family == AF_INET) {
    struct sockaddr_in *s = (struct sockaddr_in *)&addr;
    port = ntohs(s->sin_port);
    inet_ntop(AF_INET, &s->sin_addr, ipstr, sizeof ipstr);
} else { // AF_INET6
    struct sockaddr_in6 *s = (struct sockaddr_in6 *)&addr;
    port = ntohs(s->sin6_port);
    inet_ntop(AF_INET6, &s->sin6_addr, ipstr, sizeof ipstr);
}

printf("Peer IP address: %s\n", ipstr);

Getting the source address of an incoming socket connection