from run import app

if __name__ == "__main__":
    app.run(threaded=True, debug=True)

Error on request:
Traceback (most recent call last):
  File "/Library/Python/2.7/site-packages/werkzeug/serving.py", line 209, in run_wsgi
execute(self.server.app)
  File "/Library/Python/2.7/site-packages/werkzeug/serving.py", line 200, in execute
write(data)
  File "/Library/Python/2.7/site-packages/werkzeug/serving.py", line 175, in write
self.send_header('Server', self.version_string())
 File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/BaseHTTPServer.py", line 401, in send_header
self.wfile.write("%s: %srn" % (keyword, value))
IOError: [Errno 32] Broken pipe

from flask import Flask, render_template
from flask_cors import CORS

app = Flask(__name__)
CORS(app)
@app.route('/demo')
def webMap():
    return render_template('demo3.html')

if __name__ == '__main__':
    app.config['DEBUG'] = True
    app.run(host='localhost', port=8090)

var map = L.map('map1').setView([51.506725, -0.076486], 12);

    L.tileLayer('https://api.tiles.mapbox.com/v4/{id}/{z}/{x}/{y}.png?access_token={accessToken}', {
    attribution: 'Map data &copy; <a href="http://openstreetmap.org">OpenStreetMap</a> contributors, <a href="http://creativecommons.org/licenses/by-sa/2.0/">CC-BY-SA</a>, Imagery © <a href="http://mapbox.com">Mapbox</a>',
    maxZoom: 18,
    id: 'mapbox.streets',
    accessToken: '*************************'
}).addTo(map);


//add start marker to map and delete old marker
var startmarker = null;

map.on('click', function (e) {
    if (startmarker !== null) {
        map.removeLayer(startmarker);
    }
     startmarker = L.marker(e.latlng, {
         title: "Start Point",
     }).addTo(map);
    startcoords = e.latlng.lng.toString() + "&" + e.latlng.lat.toString();
    startmarker.bindPopup("Start " + startcoords);
});


//add end marker to map and delete old marker

var endmarker = null;
map.on('contextmenu', function (e) {
    if (endmarker !== null) {
        map.removeLayer(endmarker);
    }
     endmarker = L.marker(e.latlng, {
         title: "End Point",
     }).addTo(map);
    endcoords = e.latlng.lng.toString() + "&" + e.latlng.lat.toString();
    endmarker.bindPopup("End " + endcoords);
    coords = startcoords+"&"+endcoords;
});

// choose query type, click button & Ajax call to API server

$("#button").click(function() {
    var val = $('input[name=query]:checked').val()
    if (val == 'route') {
        stuff = $.ajax({
            url: "http://127.0.0.1:5000/route&"+coords,
            type: "GET",
            dataType: "json" ,
        })
        .done(function( json ) {
            alert(JSON.stringify(stuff));  // trying to JSON back will work out how to display it after I get some data returned
        })
        .fail(function( xhr, status, errorThrown ) {
            alert( "Sorry, there was a problem!");
            console.log( "Error: " + errorThrown );
            console.log( "Status: " + status );
            console.dir( xhr );
        })
        .always(function( xhr, status ) {
            alert( "The request is complete!" );
        });