Q: For what purpose does the server listen on TCP?

[Inve1951]

I'm meaning to have nginx listen on the game ports on TCP to have it automatically select the correct files to serve (fastdl). This setup would have a couple of benefits for my specific circumstances. Turns out cod4x already occupies TCP.

Why? And what are the implications of removing it?
I was under the impression that the game only needs UDP.

The code comments don't explain it and git history doesn't go back far enough to learn from it either.

[AlexanderCurl]

We are sending heartbeats to the master server over TCP, UDP is for game client connections.

For fastdl, you can do something like this:

server {
    listen 80;
    listen [::]:80;

    server_name <your.domain.here>;
    root <your/cod4/root/directory/here>;

    location / {
        # try to serve file directly, fallback to front controller
	deny all;
    }

    location ~* "\.(ff|iwd)$" {
        # Just allow the .ff and .iwd files to download from the server
	allow all;
    }

    #location ~ "/$" {
        # This setting you can browse the files in the browser, I turned off.
	#autoindex on; 
    #}

    error_log /var/log/nginx/fastdl_error.log;
    access_log /var/log/nginx/fastdl_access.log;
}

Obviously replace the necessary bits to fit your needs.

[Inve1951]

If it's only for outgoing traffic (sending heartbeats) then why is it listening on TCP?

CoD4x_Server/src/sys_net.c

Lines 3257 to 3280 in 89c4cf6

	/*
	==================
	Only for Stream sockets (TCP)
	A TCP connection request has been received #1
	Try to accept this request
	==================
	*/
	__optimize3 __regparm3 qboolean NET_TcpServerConnectRequest(netadr_t* net_from, fd_set *fdr){
	struct sockaddr_storage from;
	socklen_t fromlen;
	int conerr;
	net_from->sock = INVALID_SOCKET;
	int socket;
	ioctlarg_t _true = 1;
	char errstr[256];
	if(tcp_socket != INVALID_SOCKET && FD_ISSET(tcp_socket, fdr))
	{
	fromlen = sizeof(from);
	socket = accept(tcp_socket, (struct sockaddr *) &from, &fromlen);

sudo lsof -i tcp | grep cod4x18 confirms that it's actually listening.

Does this codebase implement the master server?

Regarding nginx, I was hoping to do this:

server {
        listen 28960;
        listen 28961;
        listen 28962;
        listen 28963;
        # ....

        root /some/path/$server_port;

        location ~ \.(ff|iwd)$ {
                try_files $uri =404;
        }

        location / { return 404; }
}

Reason being that multiple cod4x instances use the same mod, but with 1 small .iwd file dynamically generated per instance per match at runtime, so they need their own file location. I still want players to reuse the other files so they don't have to download/store as much (and redownload much of it when the mod changes). This nginx config would allow for minimal manual labor (merely adding/editing a listen directive) when adding servers or changing ports. Everything else is dealt with by CI/CD.

Using the game's port makes this automagically select the correct file location. But currently the game already listens on it so it doesn't work.

[AlexanderCurl]

You probably can use nginx upstream module, so you don't have to use $server_port as a variable here.
https://nginx.org/en/docs/http/ngx_http_upstream_module.html