I have a client/server application where each client has to send an ID and a password before they can actually start the communication.
Is that secure enough? Or should I also encrypt and decrypt the byte arrays? Why is the Id and password way unsafe or safe? And would it be better to encrypt the sent data?
It depends on the type of transmition. If it is wi-fi then yes, if it is on a LAN network there's no need, if it is a safe connection. But it wont hurt to put some security
If you just encrypt the data you are revealing some information about what it is been sent