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Subscribe GetNodes

Since we are connected successfully to the Watchtower service, we can stream down available nodes from the HCS. See the protobuf definition.

Payload Static Reference
export interface FileID {  'shardNum'?: (number | string | Long);  'realmNum'?: (number | string | Long);  'fileNum'?: (number | string | Long);}export interface GetNodesQuery {  'fileId'?: (FileID | null);  'limit'?: (number);}export interface SubscribeGetNodesPayload {  subscribe: string;  body: GetNodesQuery;}const subscribeTopicRoute = `/com.hedera.mirror.api.proto.NetworkService/getNodes`;const payloadBody: GetNodesQuery = {  fileId: {    fileNum: '101' // The ID of the address book file on the network. Can be either 101 or 102.  },  limit: 100 // The maximum number of node addresses to receive before stopping. If not set or set to zero it will return all node addresses in the database.}const payload: SubscribeGetNodesPayload = {  subscribe: subscribeTopicRoute,  body: payloadBody}
Payload breakdown

To subscribe this stream, our payload should match reference protobuf definition.

View Definition 
/** * Request object to query an address book for its list of nodes */message AddressBookQuery {    /**     * The ID of the address book file on the network. Can be either 0.0.101 or 0.0.102.     */    .proto.FileID file_id = 1;    /**     * The maximum number of node addresses to receive before stopping. If not set or set to zero it will return all node addresses in the database.     */    int32 limit = 2;}

By looking into the defination, we can see that we need to provide a FileID and limit (optional) to get the latest messages.

For forming the payload, we should also be aware of basic_types.proto used in the defination.

View Definition
//** * The ID for a file  */message FileID {    /**     * The shard number (nonnegative)     */    int64 shardNum = 1;    /**     * The realm number (nonnegative)     */    int64 realmNum = 2;    /**     * A nonnegative File number unique within its realm     */    int64 fileNum = 3;}

All we need is to build a payload as below:

import React, { useEffect, useState } from "react";import io from 'socket.io-client';function StreamingInit () {  // Make sure you match the url for testnet/mainnet   const demoFileId = `102`; // The ID of the address book file on the network. Can be either 101 or 102.  const watchtowerURL = `wss://<WATCHTOWER_URL>?api_key=<ARKHIA_API_KEY>`;  const socket = io(watchtowerURL);  const [socketStatus, setSocketStatus] = useState(``);  const [socketConnect, setSocketConnect] = useState(false);  // Available services in page 2 of these docs  const subscribeGetNodesRoute = `/com.hedera.mirror.api.proto.NetworkService/getNodes`;  const getSubscriptionPayload =  (file_id: string, limit: string) => {      const subscriptionPayload = {          subscribe: subscribeGetNodesRoute,          body: {              fileId: {                  fileNum: file_id // The ID of the address book file on the network. Can be either 101 or 102.              },              limit // The maximum number of node addresses to receive before stopping. If not set or set to zero it will return all node addresses in the database.          }      };  };  const subscribeGetNodes = () => {      const requestPayload =  getSubscriptionPayload(demoFileId , `100`); // get latest 100      socket.emit(`subscribe`, requestPayload, (msg: any) => {                     console.log(`GetNodes streaming down...`);          socket.on(msg.listeners.data, function (message: any) {              console.log(message)          });          socket.on(msg.listeners.error, function (message: any) {              setSocketError(message);              console.log(`Error`);              console.log(message)          });      });  };  useEffect(() => {      socket.on(`connect`, () => {          setSocketConnect(true);          socket.on(`status`, (msg) => {              console.log(`status`, msg);              setSocketStatus(`Watchtower is successfully connected`);          });          socket.emit(`list-services`, (services: any) => {              console.log(`Listing available services`, services);          });      });      socket.on(`disconnect`, (msg: any) => {          setSocketConnect(false);          setSocketStatus(`Watchtower is disconnected.`)          console.log(`Disconnected.`)      });      socket.on(`error`, (message: any) => {          setSocketConnect(false);          console.error(message);          setSocketStatus(message)      })  }, [socket]);  return (      <>          <div>              {                  socketStatus && (                      <>                          <h6>Watchtower status</h6>                          <div>{socketStatus}</div>                      </>                  )              }              {                  socketConnect &&  (                      <>                         <button onClick={subscribeGetNodes}>                      </>                  )              }          </div>      </>  );}export default StreamingInit;