server.js

// Use to serve a raw MPEG-TS over WebSockets
// For example: ffmpeg -> server -> browser

const path = require("path");
const { spawn } = require("child_process");
const { createSocket } = require("dgram");

const TelloSDK = require("./lib/tello-sdk");

const ws = require("ws");
const express = require("express");
const app = express();

const HOST = "localhost";
const PORT = 3000;
const PORT2 = 3001;

const telloSDK = new TelloSDK();
// path to accept the incoming MPEG-TS stream
const TELLO_VIDEO_PORT = telloSDK.videoPort;
const TELLO_HOST = telloSDK.host;

app.use(express.static(path.join(__dirname, "public")));

app.post("/streamon", async (req, res) => {
  console.log("Starting stream.");
  await telloSDK.sendCommand("command");
  await telloSDK.sendCommand("streamon");
  res.end();
});

app.post("/streamoff", async (req, res) => {
  console.log("Stopping stream.");
  await telloSDK.sendCommand("command");
  await telloSDK.sendCommand("streamoff");
  res.end();
});

app.get("/battery", async (req, res) => {
  await telloSDK.sendCommand("command");
  const batteryLevel = await telloSDK.sendCommand("battery?");
  res.send(batteryLevel);
});

app.post("/tellostream", (req, res) => {
  res.connection.setTimeout(0);

  console.log(
    `Stream Connected: ${req.socket.remoteAddress}:${req.socket.remotePort}`
  );

  req.on("data", function (data) {
    streamSocket.broadcast(data);
  });

  req.on("end", function () {
    console.log(
      `Stream Disconnected: ${req.socket.remoteAddress}:${req.socket.remotePort}`
    );
  });
});

// HTTP Server to accept incoming MPEG-TS Stream
const server = app.listen(PORT, HOST, () => {
  const host = server.address().address;
  const port = server.address().port;
  console.log(`Server started at http://${host}:${port}/`);
});

// Websocket Server to send video data
const streamSocket = new ws.Server({ server: server });
const commandSocket = new ws.Server({ port: PORT2 });

streamSocket.broadcast = function (data) {
  streamSocket.clients.forEach(function each(client) {
    if (client.readyState === ws.OPEN) {
      client.send(data);
    }
  });
};

commandSocket.broadcast = function (data) {
  commandSocket.clients.forEach(function each(client) {
    if (client.readyState === ws.OPEN) {
      client.send(data);
    }
  });
};

console.log("starting ffmpeg");
// ffmpeg -i udp://192.168.10.1:11111 -f mpegts -codec:v mpeg1video -s 640x480 -b:v 800k -r 20 -bf 0 http://127.0.0.1:8081/tellostream
const ffmpeg = spawn("ffmpeg", [
  "-hide_banner",
  "-i",
  `udp://${TELLO_HOST}:${TELLO_VIDEO_PORT}`,
  "-f",
  "mpegts",
  "-codec:v",
  "mpeg1video",
  "-s",
  "640x480",
  "-q",
  "4", // 1 to 31
  "-b:v",
  "10m",
  // '800k',
  "-bf",
  "0",
  // '-r',
  // '20',
  `http://${HOST}:${PORT}/tellostream`,
]);

ffmpeg.stderr.on("data", (data) => {
  console.log(`stderr: ${data}`);
});

ffmpeg.on("close", (code) => {
  console.log(`child process exited with code ${code}`);
});

// Safely fill ffmpeg
const exitHandler = (options) => {
  if (options.cleanup) {
    ffmpeg.stderr.pause();
    ffmpeg.stdout.pause();
    ffmpeg.stdin.pause();
    ffmpeg.kill();
  }
  if (options.exit) {
    process.exit();
  }
};

process.on("exit", exitHandler.bind(null, { cleanup: true }));
process.on("SIGINT", exitHandler.bind(null, { exit: true }));
process.on("SIGUSR1", exitHandler.bind(null, { exit: true }));
process.on("SIGUSR2", exitHandler.bind(null, { exit: true }));
process.on("uncaughtException", exitHandler.bind(null, { exit: true }));

const droneState = createSocket("udp4");
droneState.on("error", (err) => {
  console.log(`server error:\n${err.stack}`);
  droneState.close();
});
droneState.on("message", (state) => {
  commandSocket.broadcast(state.toString());
});
droneState.bind(8890);

commandSocket.on("connection", function connection(ws) {
  ws.on("message", function incoming(message) {
    telloSDK.sendCommand(message);
    console.log("received: %s", message);
  });
});