add error handling for individual devices, prevent crash if one device throws error

* individual setups should run in a domain, so we can catch errors individually
* add feature to README.md

Author: iona5

README.md

@@ -34,6 +34,8 @@ When this option is set, airsonos skips teh autodiscovery part and tries to conn
 specified in <device_list>. A Sonos device is specified by its IP. 
 Optionally you can set also its TCP port if the device is set to not use the default port (1400).
 
+As long as airsonos is able to connect to at least one device, it will not end itself.
+
 This is the syntax:
 ```
 airsonos --devices SONOS1_IP[:SONOS1_PORT][,SONOS2_IP[:SONOS2_PORT][,...]]

lib/main.js

@@ -110,17 +110,35 @@ if (flags.get('version')) {
   diag();
 
 } else if (flags.get('devices').length > 0) {
-  var useDevices = flags.get('devices');
-  for (var i = 0; i < useDevices.length; i++) {
-    var ipPortSplit = useDevices[i].split(':');
+
+  var deviceArguments = flags.get('devices');
+  for(var i = 0; i < deviceArguments.length; i++) {
+
+    var deviceArg = deviceArguments[i];
+
+    // set up a domain to catch errors from setting up individual
+    // devices. For example it catches the timeout when non-existing IPs
+    // are entered.
+    var setupDomain = require('domain').create();
+    setupDomain.on('error', function(err) {
+      console.error('Error on setting up device "' + deviceArg + '": ' + err);
+    });
+
     var sonosDevice;
+
+    // Check if the argument contains a port specifier
+    var ipPortSplit = deviceArg.split(':');
     if (ipPortSplit.length > 1) {
       sonosDevice = new sonos.Sonos(ipPortSplit[0], ipPortSplit[1]);
     } else {
-      sonosDevice = new sonos.Sonos(useDevices[i]);
+      sonosDevice = new sonos.Sonos(deviceArg);
     }
 
-    setupSonos(sonosDevice, 'Sonos' + i);
+    // run the setup in a domain so we can catch errors for each device
+    // individually:
+    setupDomain.run(function() {
+      setupSonos(sonosDevice);
+    });
   }
 
 } else {