socket_server.js

const net = require('net');

// simple HTTP server using TCP sockets
var fs = require('fs');
var locations = {}; // current latitude, current longitude, destination latitude, destination longitude

function parsePOSTRequest(req) { // returns the request's body as a JSON
    const bodyIndex = r.indexOf("\n\r");
    const reqBody = r.substring(bodyIndex+3, r.length);
    let keyIndex = 0;
    let equalIndex = 0;
    let ampersandIndex = 0;
    let isDone = false;
    let parsedRespJSON = {};
    while(!isDone) {
        equalIndex = reqBody.indexOf('=', equalIndex+1);
        ampersandIndex = reqBody.indexOf('&', ampersandIndex+1);
        let key = reqBody.substring(keyIndex, equalIndex);
        let value;
        if (ampersandIndex == -1) {
            // take from last '=' character till end of string if last one, do not use ampersand index
            value = reqBody.substring(equalIndex+1, req.length)
            isDone = true; // exit the loop since we are done parsing
        }
        else {
            key = reqBody.substring(keyIndex, equalIndex) // bet. prev ampersand and equal we have the key
            keyIndex = ampersandIndex + 1;
            value = reqBody.substring(equalIndex+1, ampersandIndex) // bet. equal and ampersand we have value
        }
        parsedRespJSON[key] = value;
    }
    return parsedRespJSON;
}

var server = net.createServer(function(socket) {
    socket.on('data', function(data) {
        //console.log('Received: ' + data);
        r = data.toString();
        // console.log(r);
        if(r.substring(0,12) == "GET /compass") {
            console.log('OK');
            socket.write("HTTP/1.1 200 OK\n");
            fs.readFile('compass.html', 'utf8', function(err, contents) {
                socket.write("Content-Length:"+contents.length);
                socket.write("\n\n"); // two carriage returns
                socket.write(contents);
                
            })
        }
        else if(r.substring(0,14) == "GET /locations") {
            console.log('sending locations');
            socket.write("HTTP/1.1 200 OK\n");
            let JSONContents = JSON.stringify(locations);
            socket.write("Content-Length:"+JSONContents.length);
            socket.write("\n\n"); // two carriage returns
            socket.write(JSONContents);
            console.log(JSONContents);
        }
        else if(r.substring(0,3) =="GET"){
            console.log('OK');
            socket.write("HTTP/1.1 200 OK\n");
            fs.readFile('leaflet_test.html', 'utf8', function(err, contents) {
                socket.write("Content-Length:"+contents.length);
                socket.write("\n\n"); // two carriage returns
                socket.write(contents);
                
            })
        }
        else if(r.substring(0,4)=="POST") {
            console.log('recieved POST');
            locations = parsePOSTRequest(r); // parses body of the request to get the current and destination locations
            console.log(locations);
            socket.write('HTTP/1.1 200 OK\n');
            socket.write("Content-Length:" + 0);
            socket.write("\n\n");
        }
    });
    
    socket.on('close', function() {
        console.log('Connection closed');
    });

    socket.on('end', function() {
        console.log('client disconnected');
     });

    socket.on('error', function() {
        console.log('client disconnected');
     });
});
server.listen(8080, function() { 
    console.log('server is listening on port 8080');
});