Question

I have a TCP Server/Client where the Server listens on port 5000 and the Client outgoing port is 39000.

I have Stunnel set up on the Server:

[custom]
accept  = 6000
connect = 5000

… so it accepts connections on port 6000 and redirects it to 5000 (which my Server.c is listening on).

I tried to set up STunnel on the Client in the following way:

[custom_cl]
accept = 39000
connect = 192.168.1.3:6000

…so it accepts any data from port 39000 and sends it to the Server (let’s say it’s at 192.168.1.3) at port 6000.

My client has this code:

client_addr.sin_family = AF_INET;
client_addr.sin_port = htons(39000);
client_addr.sin_addr.s_addr = inet_addr("0.0.0.0");
bzero(&(client_addr.sin_zero),8);

if (bind(sock, (struct sockaddr *)&client_addr, sizeof(struct sockaddr))
                                                               == -1) {
     perror("Unable to bind");
     exit(1);
     }

…so that it will always send out on port 39000. My problem is that I receive an “Unable to bind: Address already in use” because (I’m guessing) STunnel is listening on port 39000. What should I be doing?

Answer 1

You don’t need to bind a socket for outgoing connection (unless you know what you are doing and what for). You just need to create a socket and call connect(). You pass localhost (or 127.0.0.1) as destination address and 39000 as destination port.