小游戏压测，有规律的websocket断掉，是什么原因？

nodejs服务器端有时会显示

(node:3073) UnhandledPromiseRejectionWarning: Error: socket hang up

    at createHangUpError (_http_client.js:331:15)

    at TLSSocket.socketOnEnd (_http_client.js:423:23)

    at emitNone (events.js:111:20)

    at TLSSocket.emit (events.js:208:7)

    at endReadableNT (_stream_readable.js:1064:12)

    at _combinedTickCallback (internal/process/next_tick.js:138:11)

    at process._tickCallback (internal/process/next_tick.js:180:9)

(node:3073) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (rejection id: 8)