server.js

fs = require('fs');
http = require('http');
url = require('url');
exec = require('child_process').execSync
http.createServer(function(req, res){
  var request = url.parse(req.url, true);
  if (request.pathname.split('/')[1] === 'tile') {
    var tile = request.pathname.split('/')[2].split('.')[0].split('-')
    res.writeHead(200, {'Content-Type': 'image/png' });
    var img
    if(fs.existsSync(__dirname+'/tile/'+tile[0]+'-'+tile[1]+'-'+tile[2]+'.png')){
      img = fs.readFileSync(__dirname+'/tile/'+tile[0]+'-'+tile[1]+'-'+tile[2]+'.png', 'binary')
    } else {
      console.log('write: '+tile[0]+'/'+tile[1]+'/'+tile[2])
      img = exec('geotype ./dc.json -p -f 0 -m 2 -t '+tile[0]+'/'+tile[1]+'/'+tile[2]) 
      fs.writeFileSync(__dirname+'/tile/'+tile[0]+'-'+tile[1]+'-'+tile[2]+'.png',img)
    }
    res.end(img, 'binary');
  } else { 
    res.writeHeader(200, {"Content-Type": "text/html"});  
    res.write(fs.readFileSync(__dirname+'/index.html'));
    res.end();
  }
}).listen(8080, '127.0.0.1');
console.log('listening 127.0.0.1:8080');