printserver.js

//
// printserver.js
//    WebSocket print server
//
// dependencies:
//    npm install printer ws
//    Windows
//       npm install --global windows-build-tools
//    Linux
//       sudo apt-get install node-gyp
//       sudo apt-get install libcups2-dev
//
// Neil Gershenfeld 
// (c) Massachusetts Institute of Technology 2017
// 
// This work may be reproduced, modified, distributed, performed, and 
// displayed for any purpose, but must acknowledge the mods
// project. Copyright is retained and must be preserved. The work is 
// provided as is no warranty is provided, and users accept all 
// liability.
//
// check command line
//
if (process.argv.length < 4) {
   console.log("command line: node printserver.js client_address server_port")
   process.exit(-1)
   }
//
// start server
//
var client_address = process.argv[2]
var server_port = process.argv[3]
console.log("listening for connection from client address "+client_address+" on server port "+server_port)
//
// requires
//
var printer = require("printer")
var WebSocketServer = require('ws').Server
//
// start WebSocket server
//
wss = new WebSocketServer({port:server_port})
//
// handle connection
//
wss.on('connection',function(ws) {
   //
   // check address
   //
   if (!ws._socket.remoteAddress) {
      console.log("connection rejected from "+ws._socket.remoteAddress)
      ws.send('socket closed')
      ws.close()
      }
   else {
      console.log("connection accepted from "+ws._socket.remoteAddress)
      // get printer list
      function getPrinterList() {
         var printerList = []
         var printers = printer.getPrinters()
         if (printers && printers.length) {
            var i = printers.length
            for (i in printers) {
               var pr = printers[i]
               printerList.push(pr.name)
               }
            }
         var printerListObj = {}
         printerListObj['printerList'] = printerList
         printerListObj['default'] = printer.getDefaultPrinterName()
         return printerListObj
         }

       ws.send(JSON.stringify(getPrinterList()))
       ws.send('socket opened')
      }
   //
   // handle messages
   //
   var cancel
   var pagesPrinted
   ws.on("message",function(msg) {
      console.log(msg)
      //
      // cancel job
      //
      if (msg == 'cancel') {
         cancel = true
         }
      //
      // start job
      //
      else {
         var job = JSON.parse(msg)
         console.log('writing '+job.name+' (length '+job.contents.length+') to printer '+job.printer)
         cancel = false
         print()
         //
         // print all
         //
         function print() {
            console.log(job.contents)
            printer.printDirect({data:job.contents,type:'RAW',
             printer:job.printer,success: function (jobID) {
               console.log("sent to printer with ID: "+jobID)
               check_process()
               //
               // Check process
               //
               function check_process() {
                  var jobInfo
                  try {
                     jobInfo = printer.getJob(job.printer,jobID)
                     }
                  catch (err) {
                     ws.send('done')
                     return
                     }
                  console.log("current job info:"+
                     JSON.stringify(jobInfo))
                  if (jobInfo.status.indexOf('PRINTED') !== -1) {

                     var ret = printer.setJob(job.printer,
                        jobID,'CANCEL')

                     ws.send('done')
                     return
                     }
                  //
                  // cancel
                  //
                  if (cancel) {
                     console.log('cancelling...')
                     ws.send('cancel')
                     var ret = printer.setJob(job.printer,
                        jobID,'CANCEL')
                     console.log("cancelled: "+ret)
                     }
                  //
                  // continue
                  //
                  else {
                     ws.send(jobInfo.status[0])
                     setTimeout(check_process,1000)
                     }
                  }
               }, error: function(err) {
                  console.log(err)
                  ws.send('error '+err)
                  }
               })
            }
         }
      })
   //
   // close
   //
   ws.on("close",function() {
      console.log("connection closed")
      })
   })