3128 is a common http/s proxy sure, but so is 8080, and I've seen 80 a few times too. 1080 is often default for socks, but I've also seen places where it's 108

3128 is a common http/s proxy sure, but so is 8080, and I've seen 80 a few times too. 1080 is often default for socks, but I've also seen places where it's 1085 (for socks5 -- 1084 for socks4) Ultimately it can be whatever you want.