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Contacting API with Protobuf

Import Compiled .proto Files​

In order to import and use the compiled .proto files in our code, we need to install the corresponding Protobuf library in our programming langauge of choice.

npm i protobufjs

Establish Secure Connection​

Encode Decode Messages​

Putting It Altogether​

var tls = require('tls');
var pb = require('./pb.compiled.js');
var creds = require('./credentials.json');

var { accountId: ctidTraderAccountId, accessToken } = creds;
var { log } = console;
var nameByType = constructConvenientMap();

const host = 'live.ctraderapi.com';
const socket = tls.connect(
  {
    host: host,
    port: 5035,
    servername: host,
  },
  () => {
    log(
      `connection open (${socket.authorized ? 'authorized' : 'unauthorized'})`,
    );
  },
);

socket.on('connect', () => {
  log('connect');
  var rdyBuf = constructMsg(pb.ProtoOAApplicationAuthReq, {
    clientId: creds.clientId,
    clientSecret: creds.clientSecret,
  });
  socket.write(rdyBuf);
});

socket.on('data', (buf) => {
  log('data received');
  var msg = deconstructMsg(buf);
  log(msg);
});

socket.on('error', (error) => {
  log('error:', error.message); // error.code, error.errno,
});

socket.on('close', (hadError) => log('close', { hadError }));

// async infinite loop
(async () => {
  while (true) {
    await new Promise((r) => setTimeout(r, 1000));
  }
})();

function deconstructMsg(buf) {
  var protoMsg = pb.ProtoMessage.decode(buf);
  var PayloadMsg = pb[nameByType[protoMsg.payloadType]];
  protoMsg.payload = PayloadMsg.decode(protoMsg.payload);
  return protoMsg;
}

function constructMsg(Msg, payload) {
  var payloadMsg = Msg.create(payload);
  var payloadMsgEncoded = Msg.encode(payloadMsg);

  var protoMsg = pb.ProtoMessage.create({
    payloadType: payloadMsg.payloadType,
    payload: payloadMsgEncoded.finish(),
  });

  var protoMsgEncoded = pb.ProtoMessage.encode(protoMsg);

  var dataLen = protoMsgEncoded.len;
  var data = protoMsgEncoded.finish();

  var lengthBytes = Buffer.alloc(4);
  lengthBytes.writeUInt32BE(dataLen, 0);

  var totLen = lengthBytes.length + data.length;
  var rdyBuf = Buffer.concat([lengthBytes, data], totLen);

  return rdyBuf;
}

function constructConvenientMap() {
  const chgcase = (s) =>
    'ProtoOA' +
    s
      .split('PROTO_OA_')[1]
      .split('_')
      .map((i) => i.toLowerCase())
      .map((i) => [i[0].toUpperCase(), ...i.slice(1)].join(''))
      .join('');

  var o = pb.ProtoOAPayloadType;
  var payloadTypes = Object.keys(o).map((k) => [o[k], chgcase(k)]);
  var nameByType = Object.fromEntries(payloadTypes);

  return nameByType;
}