Connect AIS by TCP or UDP protocol ?
This short article is applicable to ANY onboard setup involving an AIS receiver connecting to one or more tablets / phones / marine plotters using WiFi
If you have several devices connected by TCP protocol at the same time to your AIS WiFi you could run into problems. Flakey, unreliable connections.
Without getting too technical, the reason is this.. The TCP protocol acts and behaves like a private phone connection between 2 parties, The AIS WiFi sending out NMEA can only connect with ONE instance (ie phone, tablet, plotter) at one time on one TCP channel. If you have several devices set on that single connection.. you may be OK if the main device you are using is the only one that's being used. If you have other connected devices switched on there are likely to be problems. (It is possible that the transmitting WiFi has several TCP channels that can be used all at once ? In which case set one device per channel)
"Up to 7 devices can connect using UDP. TCP/IP is a one to one connection format. PCs, MACs, Android, Linux and iPhone/iPad are all compatible." Digital Yacht iAISTX
The UDP protocol is totally different. It acts like the Brexit Man, Steve Bray, standing there shouting into his megaphone. Anyone within range can hear his broadcast.. With UDP you can tune multiple WiFi devices into this broadcast with no problem.
So if you use multiple phones, tablets, etc around the boat to keep a check on AIS targets, UDP protocol is probably the way to go.
In depth study of the different protocols here: