How do applications coexist over TCP and UDP?

Question

Which is better and why ??

Answer 1

Question itself is related to Applications, it is very generic question related to TCP/IP model.
Application sits top of the transport layer protocol. It doesn't bother about transport. Application focus on "what is data" not about "How it is reached" .

Answer 2

Each application running over TCP or UDP distinguishes itself from other applications using the service by reserving and using a 16-bit port number. Destination and source port numbers are placed in the UDP and TCP headers by the originator of the packet before it is given to IP, and the destination port number allows the
packet to be delivered to the intended recipient at the destination system.