Port forwarding for Zookeeper (to 5 remote hosts behind a firewall)

configuration-map-krb.json

{ 
  "88" : {
      "auth-1" : 8088
  }
}

configuration-map-socket.json

{
  "2181": {
    "type": "socket",
    "members": [
      { "hostname": "kafka-1", "port": 30991 },
      { "hostname": "kafka-2", "port": 30992 },
      { "hostname": "kafka-3", "port": 30993 },
      { "hostname": "kafka-4", "port": 30994 },
      { "hostname": "kafka-5", "port": 30995 }
    ]
  }
}

krb5-tcp.js

/**
 * Kerberos Socket Proxy
 **/

// Need to use NET (not http)
const net = require("net");
const fs = require("fs");

// The total retry count starts at 0 and goes to 5
var retry = 0;

// Load the configuration details for the ports (mapping to a localhost port mapping)
var jsonConfig = JSON.parse(
  fs.readFileSync("configuration-map-krb.json", "utf8")
);

/**
 * socket server for Zookeeper port forwarding...
 * must have allowHalfOpen to be true
 */
const server = net
  .createServer({ allowHalfOpen: true}, socket => {
    socket.on('end', () => {
      console.log('server client disconnected');
    });

    // Get the remoteAddress indicators
    console.log("socket remote address: ", socket.localAddress);
    console.log("socket remote port: ", socket.localPort);

    socket.setTimeout(3000);

    var ipAddr = socket.localAddress;

    if (ipAddr != null && ipAddr.startsWith("127.0.0.")) {
    
      serverId = ipAddr.replace("127.0.0.", "");

      socket.on("data", function(data) {
        
        // Creates a socket
        var client = new net.Socket();
        client.connect(8088, "localhost", function() {
          console.log("Connected to backend");
          client.write(data);
        });

        //Writes the data from the port back
       
        client.on("data", function(chunk) {
          console.log("Received: ",chunk );
          socket.write(chunk);
          
          // kill server socket | client socket after server's response
          client.end(); 
          socket.end();
        });

        client.on("close", function() {
          console.log("Connection closed");
        });
        
      });
      
    } else {
      socket.end("Forbidden\n");
    }
  })
  .on("error", err => {
    // Check for the error https://nodejs.org/dist/latest-v10.x/docs/api/net.html#net_identifying_paths_for_ipc_connections
    if (err.code === "EADDRINUSE" && retry < 5) {
      retry++; // Keep from infinite repeats
      console.log("Address in use, retrying...");
      setTimeout(() => {
        server.close();
        server.listen(88, "localhost");
      }, 1000);
    } else if (retry == 5) {
      console.error("There is an error in the startup - address in use");
    } else {
      throw err;
    }
  });

// We are going to loop over all services and open servers
// Repeating this server.listen for a variety of addresses, defaults to only 127.0.0.1
// must map to 0.0.0.0 and limit to only IPs from 127.0.0.0
server.listen(88, "0.0.0.0", () => {
  console.log("opened server on", server.address());
});

proxy_socket.js

/**
 * Zookeeper Socket Proxy
 **/

// Need to use NET (not http)
const net = require("net");
const fs = require("fs");

// The total retry count starts at 0 and goes to 5
var retry = 0;

// Load the configuration details for the ports (mapping to a localhost port mapping)
var jsonConfig = JSON.parse(
  fs.readFileSync("configuration-map-socket.json", "utf8")
);

/**
 * socket server for Zookeeper port forwarding...
 * must have allowHalfOpen to be true
 */
const server = net
  .createServer({ allowHalfOpen: true}, socket => {
    socket.on('end', () => {
      console.log('server client disconnected');
    });


    // Get the remoteAddress indicators
    console.log("socket remote address: ", socket.localAddress);
    console.log("socket remote port: ", socket.localPort);

    socket.setTimeout(3000);

    var ipAddr = socket.localAddress;

    if (ipAddr != null && ipAddr.startsWith("127.0.0.")) {
      

      serverId = ipAddr.replace("127.0.0.", "");

      socket.on("data", function(data) {
        
        console.log("the four letter command that is forwarded: " + data);

        var mappingPort = jsonConfig[socket.localPort].members[parseInt(serverId)-1]["port"];
        console.log("The Mapping Port is : " + mappingPort);
                
        // Creates a socket
        var client = new net.Socket();
        client.connect(mappingPort, "localhost", function() {
          console.log("Connected to backend");
          client.write(data);
        });

        //Writes the data from the port back
       
        client.on("data", function(chunk) {
          console.log("Received: ",chunk );
          socket.write(chunk);
          
          // kill server socket | client socket after server's response
          client.end(); 
          socket.end();
        });

        client.on("close", function() {
          console.log("Connection closed");
        });
        
      });
      
    } else {
      socket.end("Forbidden\n");
    }
  })
  .on("error", err => {
    // Check for the error https://nodejs.org/dist/latest-v10.x/docs/api/net.html#net_identifying_paths_for_ipc_connections
    if (err.code === "EADDRINUSE" && retry < 5) {
      retry++; // Keep from infinite repeats
      console.log("Address in use, retrying...");
      setTimeout(() => {
        server.close();
        server.listen(2181, "localhost");
      }, 1000);
    } else if (retry == 5) {
      console.error("There is an error in the startup - address in use");
    } else {
      throw err;
    }
  });

// We are going to loop over all services and open servers
// Repeating this server.listen for a variety of addresses, defaults to only 127.0.0.1
// must map to 0.0.0.0 and limit to only IPs from 127.0.0.0
server.listen(2181, "0.0.0.0", () => {
  console.log("opened server on", server.address());
});