HTTP-port or HTTP port?

The "HTTP" is a singular adjective, so there's no need to connect the adjective with the noun. Only when there are two adjectives that modify the same verb and cannot do without one another, are they connected with a hyphen, (such as "greyish-green colour"). In this case, there's only "HTTP".

Unless, however, you are describing something with "HTTP port", such as a "HTTP-port USB". In which case, a hyphen would be correct. However, it's not very common usage:

It really depends on the context. As I say, if you are referring to "port" as the noun, then there is no need for a hyphen. If you are using "HTTP port" as an adjective, then a hyphen would be used.

In this case, port is the subject and http is the adjective; it follows that you do not hyphenate, since you would not join the subject and adjective. Hyphenation is used to combine multiple words into one, often to create an adjective or other compound word.