need an brief answer about UDP(User Datagram Protocol)! In what circumstances it helps the user?

UDP is used to send short messages or data to other comps in the network. The messages sent are not arranged in some specific way but it is sent randomely and some messages can even go missing. We studied in TCP/IP(Transmission Control Protocol) that any data sent will be checked using error controls, flow control,etc, but when sending data through UDP, these checkings are not done.
Because of this, transmission is faster. Some frames may go missing here. But to lose packets are better than delayed packets.

That is a pretty good answer. UDP is basically provides connectionless unreliable service. There are some instances when such services are also necessary !!

Eg. Streaming Real Media, etc ...

Hi KavinIsrael.

The User Datagram Protocol (UDP) is one of the core members of the Internet Protocol Suite, the set of network protocols used for the Internet. With UDP, computer applications can send messages, in this case referred to as datagrams, to other hosts on an Internet Protocol (IP) network without requiring prior communications to set up special transmission channels or data paths. UDP is sometimes called the Universal Datagram Protocol.
UDP is one out of the two transport protocols available for internet's applications, that is UDP and TCP using which, programs running on different computers on a network can send short messages known as Datagrams to one another.UDP provides very few error recovery services, offering instead a direct way to send and receive datagrams over an IP network. It is used by applications that do not require the level of service of TCP or that wish to use communications services not available from TCP.

I try to make an application that communicate server by udp. i easly send data from client to server. but there is problem when i try to send data from server to client.I make server pc as both server and client, and phone become also both server and same time client.when i send a data from phone to server, i use phone's client side and send data to server pc's server side. and when i send data from server to phone.
my code is working good in emulators. but, in real device, it dont work.
where is problem, do you think?