Understanding socket.io ping interval/timeout settings

Question

According to SO accepted answer, the ping timeout must be greater than the ping interval, but according to the examples in official socket.io docs, the timeout is less than the interval. Which one is correct?? Also, what could be the ideal values for both the settings for a shared whiteboard application where the moderator should not be able to edit the canvas when disconnected (internet drops off).

Answer 1

According to the socket.io documentation:

Among those options:

pingTimeout (Number): how many ms without a pong packet to consider the connection closed (60000)

pingInterval (Number): how many ms before sending a new ping packet (25000).

Those two parameters will impact the delay before a client knows the server is not available anymore. For example, if the underlying TCP connection is not closed properly due to a network issue, a client may have to wait up to pingTimeout + pingInterval ms before getting a disconnect event.

This leads me to believe there is no dependency on one value being greater than another. You will likely want to set a higher timeout time to allow for slow network connection to receive a response. The interval time will be the time from a failure to attempt trying again and should be set long enough to allow reconnection, but not so long you are holding the connection.

As for ideal values, this will be application specific. A few things I would consider:

• How responsive must your application be?
• How long will your application take to respond to a network request?
  • How large is the data being passed back and forth?
• How many concurrent users will you have?

These are just to name a few, for a small local application you would likely be fine with a timeout of 10000 and an interval of 5000, but this is an absolute guess. You will need to consider the previously mentioned bullet points.