UDP Server Socket Buffer Overflow

Question

I am writing a C++ application on Linux. My application has a UDP server which sends data to clients on some events. The UDP server also receives some feedback/acknowledgement

Answer 1

Having socket reading at fixed interval of four seconds definitely sets you up for losing packets. The conventional tried-and-true approach to non-blocking I/O is the de-multiplexer system calls select(2)/poll(2)/epoll(7). See if you can use these to capture/react to your other events.

On the other hand, since you are already using threads, you can just do blocking recv(2) without that four second sleep.

Read Stevens for explanation of SO_RCVBUF.

Answer 2

You can see the maximum allowed buffer size:

sysctl net.core.rmem_max

You can set the maximum buffer size you can use by:

sysctl -w net.core.rmem_max=8388608

You can also set the buffer size at run-time (not exceeding the max above) by using setsockopt and changing SO_RCVBUF. You can see the buffer level by looking at /proc/net/udp.

The buffer is used to store the UDP header and application data, rest belong to lower levels.

Answer 3

Q: Is it correct to use the same socket for sending/receiving UDP data with Mulitiple clients ?

A: Yes, it is correct.

Q: How to find the maximum number of UDP Feedback/Acknowledge Packets my application can handling without UDP Socket Buffer Overflow (since I am reading at every 4secs, if I receive lot of packets within this 4secs I might loose some packet ie., I need to find the rate : noofpackets/sec I can handle safely)?

A: The bottleneck might be the network bandwidth, or CPU, or memory. You could simply do a testing, using a client which sends ACK to the server with consecutive number, and verify whether there is packet loss at the server.