In fact, ping needs to know about dropped or out of order packets to determine how good or bad the connection is. Thus a reliable channel would invalidate this service altogether. The UDP protocol provides for non-guaranteed communication between two applications on the network. Rather it sends independent packets of data, called datagrams from one application to another. UDP is a protocol that sends independent packets of data, called datagrams from one computer to another with no guarantees about arrival.
Ports Generally speaking, a computer has a single physical connection to the network.
All data destined for a particular computer arrives through that connection. However, the data may be intended for different applications running on the computer. Through the use of ports . Data transmitted over the Internet is accompanied by addressing information that identifies the computer and the port that it's destined for. The computer is identified by its 32-bit IP address, which IP uses to deliver data to the right computer on the network.