java：客户端/服务器套接字中的 I/O 流导致随机 300 毫秒延迟

Question

I'm working on some project that requires a low latency communication between a server and a client application. Both runs on my computer so it is connected to localhost.

The data transfer via DataInputStream and DataOutputStream and the socket connection works properly, and 99% of the time the measured ping is 0ms or 1ms, however sometimes the communication gets randomly delayed by 300ms.

Normal applications like network games run fine without any "lagspikes", so I'm sure it's not an issue with my computer.

I find it very suspicious that the delay is always exactly 300ms when it occurs and 0ms or 1ms when it does not occur, so there is something happening but I can not find out what.

I logged with timestamps until figuring out it happens both at server and client at any of the

in.read();

with in being the DataInputStream so im assuming the delay is not directly in my code.

Can someone explain to me, what in Java, the I/O stream or the sockets is causing a 300ms lag and how do I solve it? The only thing I changed for server/client is

socket.setPerformancePreferences(0, 1, 0);

but it didn't change a thing.

My code is a bit big but the general structure for the relevant part of both server and client application looks like:

while(still_alive) {
  out.writeInt(data1);
  out.writeInt(data2);
  out.writeDouble(data3);
  data1 = in.readInt();
  data2 = in.readInt();
  data3 = in.readDouble();
  DoSomethingWithData(data1, data2, data3);
}

Thanks in advance!

Kaisky

Answer 1

I've found the solution!

It seems like DataInputStream and DataOutputStream are not suitable for low latency network but you should use BufferedInputStream and BufferedOutputStream instead.

It is a bit harder to use since every input is in bytes so you need to translate any int, double and String into byte arrays and translate them back, so i took a while to do that but now it works perfectly without any lag.

Answer 2

socket.setPerformancePreferences(1, 0, 2); // here latency is 0.
socket.setTcpNoDelay(true); // for client as well as server.

try this out. it will make great change. and DataOutputStream and DataInputStream work perfect with it.