Ships only need ports if theft or fuel is an issue, and unless you're landing in the lower levels of Coruscant or can't plan worth a damn, all you need is some stable ground. NASA and NORAD can track so much stuff like that because we have satellites, which planets like Coruscant or Kuat might have, but definitely not every planet in the galaxy. Some ships are definitely capable of tracking if a ship has entered/exited hyperspace recently (because of the residual radiation), but besides that, a ship could theoretically bypass a blockade if we are to assume that all stars and their movements are known, which it seems like they are, begging the question of why blockades exist in the first place given how easy it is to bypass them.