Where the datagrams are if a client does not listen to a UDP port?

Question

Hello all.

Suppose a client sends a number of datagrams to a server through my application. If my application on the server side stops working and cannot receive any datagrams, but the client still continues to send more data grams to the server through UDP protocol, where are those datagrams going? Will they stay in the server's OS data buffer (or something?)

I ask this question because I want to know that if a client send 1000 datagrams (1K each) to a PC over the internet, will those 1000 datagrams go through the internet (consuming the bandwidth) even if no one is listening to those data?

If the answer is Yes, how should I stop this happening? I mean if a server stops functioning, how should I use UDP to get to know the fact and stops any further sending?

Thanks

Answer 1

I ask this question because I want to know that if a client send 1000 datagrams (1K each) to a PC over the internet, will those 1000 datagrams go through the internet (consuming the bandwidth) even if no one is listening to those data?

Yes

If the answer is Yes, how should I stop this happening? I mean if a server stops functioning, how should I use UDP to get to know the fact and stops any further sending?

You need a protocol level control loop i.e. you need to implement a protocol to take care of this situation. UDP isn't connection-oriented so it is up to the "application" that uses UDP to account for this failure-mode.

Answer 2

UDP itself do not provide facilities to determine if message is successfully received by a client or not. You need you TCP to establish reliable connection and after it sends data over UDP.

Answer 3

The lowest overhead solution would be a keep-alive type thing like jdupont suggested. You can also change to use tcp, which provides this facility for you.