Keep Alive (clientbound)

Play 0x2C, server → client.

play · 0x2C · clientbound (server → client)

Sends a random keepAliveId that the client must echo back in a serverbound KeepAlive. The server sends it about every 15 seconds. If the client does not answer within 30 seconds the server disconnects it with a timeout.

Sent by the server, read by the client. Listen for it with client.on("KeepAlive", (data) => …) on the receiving side.

Fields

Send it

// Server side with autoKeepAlive: false.
const keepAliveId = BigInt(Date.now());
await client.sendPacket("KeepAlive", { keepAliveId });

client.on("KeepAlive", (data) => {
  if (data.keepAliveId !== keepAliveId) client.destroy();
});

The vanilla client disconnects after 20 seconds without a ping, and the server should drop clients that do not echo the ID within 30 seconds. With autoKeepAlive: true (the default) the server does all of this and emits keepAlive with the latency.

Field aliases listed under Notes are accepted as alternative keys when writing.

Source: src/Core/Versions/776/Packets/play/clientbound/KeepAlive.ts