Category: Technical

Auto-updating software

So, over the years, I’ve released a few programs (all native C/C++) which have included automatic version checking, so they can let the user know when a new version is available. I’ve always done this by making a socket connection to my web server (previously Apache, now entirely Node.js) and asking for a file which just contains a version number. Pretty simple, right? Sure!

SOCKET s = socket(AF_INET, SOCK_STREAM, 0);
connect(s, ...);
char cmd[] = "GET http://www.bigscreensmallgames.com/BestBombermanEver/version.txt HTTP/1.0\r\n\r\n";
send(s, cmd, sizeof(cmd), 0);
recv(s, ...);

And that’s about it.  Note:

• This sends a single packet, and no router’s MTU is small enough that this packet would ever be fragmented, so it is, in theory, at least according to how TCP/IP is supposed to work, guaranteed to arrive as a single packet. Not that most web servers would care…
• I don’t bother sending any headers, specifically the Host header. Why would I if this works?
• There’s a bug in the code, it’s writing the NULL character into the packet after the final line feed.

Continue reading “The horrible things people’s routers do to my packets!”