In C or C++ it is fairly simple to find the IP address of the remote end of a TCP socket.

The following example shows how to do this using the getpeername() and inet_ntoa() system calls.

int sockfd;
int len;
char * hostip;
struct sockaddr_in sin;

len = sizeof(sin);

if (0 != getpeername(sockfd, (struct sockaddr *) &sin, &len))
        perror("getpeername");
}

hostip = inet_ntoa(sin.sin_addr);

printf("client IP: %s\n", hostip);

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