Node-RED is a flow-based programming tool built-on Node.js. It provides a browser-based editor that helps users to create awesome applications by wiring different nodes. This article shares my experience of building a barcode node with Dynamsoft Barcode Reader on Windows.
Installing and Running Node RED on Windows 10
Install Node-RED:
sudo npm install -g --unsafe-perm node-red
On Windows, the default installation directory is %userprofile%\ .node-red.
Run Node-RED:
node-red
It failed when I started Node-RED for the first time. Here is the error message:
Welcome to Node-RED
===================
5 Nov 14:29:12 - [info] Node-RED version: v0.19.5
5 Nov 14:29:12 - [info] Node.js version: v8.11.3
5 Nov 14:29:12 - [info] Windows_NT 10.0.17763 x64 LE
5 Nov 14:29:13 - [info] Loading palette nodes
5 Nov 14:29:14 - [warn] rpi-gpio : Raspberry Pi specific node set inactive
5 Nov 14:29:15 - [warn] ------------------------------------------------------
5 Nov 14:29:16 - [warn] [node-red/tail] Not currently supported on Windows.
5 Nov 14:29:16 - [warn] ------------------------------------------------------
5 Nov 14:29:16 - [info] Settings file : \Users\xiao\.node-red\settings.js
5 Nov 14:29:16 - [info] Context store : 'default' [module=memory]
5 Nov 14:29:16 - [info] User directory : \Users\xiao\.node-red
5 Nov 14:29:16 - [warn] Projects disabled : editorTheme.projects.enabled=false
5 Nov 14:29:16 - [info] Flows file : \Users\xiao\.node-red\flows_DESKTOP-3PCHU10.json
5 Nov 14:29:16 - [info] Creating new flow file
5 Nov 14:29:16 - [info] Starting flows
5 Nov 14:29:16 - [info] Started flows
5 Nov 14:29:16 - [error] Uncaught Exception:
5 Nov 14:29:16 - [error] Error: listen EACCES 0.0.0.0:1880
at Object._errnoException (util.js:992:11)
at _exceptionWithHostPort (util.js:1014:20)
at Server.setupListenHandle [as _listen2] (net.js:1338:19)
at listenInCluster (net.js:1396:12)
at doListen (net.js:1505:7)
at _combinedTickCallback (internal/process/next_tick.js:141:11)
at process._tickCallback (internal/process/next_tick.js:180:9)
It seems something wrong with the default port 1880. We can use Resource Monitor to check the port usage.
I did not find 1880 in the port list. I tried a port that is in use and got a different error message:
5 Nov 14:40:00 - [info] Node-RED version: v0.19.5 5 Nov 14:40:00 - [info] Node.js version: v8.11.3 5 Nov 14:40:00 - [info] Windows_NT 10.0.17763 x64 LE 5 Nov 14:40:01 - [info] Loading palette nodes 5 Nov 14:40:01 - [warn] rpi-gpio : Raspberry Pi specific node set inactive 5 Nov 14:40:03 - [warn] ------------------------------------------------------ 5 Nov 14:40:03 - [warn] [node-red/tail] Not currently supported on Windows. 5 Nov 14:40:03 - [warn] ------------------------------------------------------ 5 Nov 14:40:03 - [info] Settings file : \Users\xiao\.node-red\settings.js 5 Nov 14:40:03 - [info] Context store : 'default' [module=memory] 5 Nov 14:40:03 - [info] User directory : \Users\xiao\.node-red 5 Nov 14:40:03 - [warn] Projects disabled : editorTheme.projects.enabled=false 5 Nov 14:40:03 - [info] Flows file : \Users\xiao\.node-red\flows_DESKTOP-3PCHU10.json 5 Nov 14:40:03 - [info] Creating new flow file 5 Nov 14:40:03 - [info] Starting flows 5 Nov 14:40:03 - [info] Started flows 5 Nov 14:40:03 - [error] Unable to listen on http://127.0.0.1:1551/ 5 Nov 14:40:03 - [error] Error: port in use
The workaround is to change the port number in %userprofile%\.node-red\settings.js. For example, we can change the default port number to 18800 and then it will work:
Building Barcode Node
Let’s create a barcode node with Dynamsoft Barcode Reader.
Use npm command to initialize a Node RED project:
npm init barcode
Add the node-red section to package.json:
"node-red": {
"nodes": {
"barcode": "barcode.js"
}
},
Install Dynamsoft Barcode Reader:
npm install dbr --save
Create barcode.js:
module.exports = function(RED) {
var dbr = require('dbr');
var barcodeTypes = 0x3FF | 0x2000000 | 0x4000000 | 0x8000000 | 0x10000000; // 1D, PDF417, QRCODE, DataMatrix, Aztec Code
function BarcodeNode(config) {
RED.nodes.createNode(this, config);
this.license = config.license;
this.template = config.template;
var node = this;
node.on('input', function(msg) {
if (msg.filename) {
dbr.initLicense(node.license);
dbr.decodeFileAsync(msg.filename, barcodeTypes, function(err, results) {
msg.payload = results;
node.send(msg);
}, node.template);
} else {
msg.payload = msg.payload.toLowerCase();
node.send(msg);
}
});
}
RED.nodes.registerType('barcode', BarcodeNode);
}
When receiving the input event, we can call the barcode decoding method by setting license and parameter templates.
Create barcode.html:
<script type="text/javascript">
RED.nodes.registerType('barcode',{
category: 'Dynamsoft',
color: '#a6bbcf',
defaults: {
name: {value:""},
license: {value:""},
template: {value: ""}
},
inputs:1,
outputs:1,
icon: "function.png",
label: function() {
return this.name||"barcode";
}
});
</script>
<script type="text/x-red" data-template-name="barcode">
<div class="form-row">
<label for="node-input-name"><i class="icon-tag"></i> Name</label>
<input type="text" id="node-input-name" placeholder="Barcode Reader">
</div>
<div class="form-row">
<label for="node-input-license"><i class="icon-tag"></i> License</label>
<input type="text" id="node-input-license" placeholder="https://www.dynamsoft.com/CustomerPortal/Portal/Triallicense.aspx">
</div>
<div class="form-row">
<label for="node-input-template"><i class="icon-tag"></i> Template</label>
<input type="text" id="node-input-template" placeholder="https://www.dynamsoft.com/help/Barcode-Reader/devguide/Template/TemplateSettingsList.html">
</div>
</script>
<script type="text/x-red" data-help-name="barcode">
<p>A simple node that read barcodes from image files.</p>
</script>
Install and test the project:
cd %userprofile%\.node-red npm install <node-red barcode project> node-red
Open http://127.0.0.1:18800/ in your web browser. Add inject node, file node, barcode node and debug node. You can set the image path in the file node:
Click barcode node to set a valid license and barcode parameter template:
Here is an example of a template:
{
"ImageParameter": {
"Name": "Custom_143301_827",
"BarcodeFormatIds": [
"OneD"
]
}
}
If you do not set a template, the default template will be used.
Run the app:
If there is something wrong with dbr.node(compatibility issue caused by Node.js version), you can use the source code to build it by yourself.
It everything works well, we can publish the module:
cd <node red barcode project> npm publish
Use the module:
cd %userprofile%\.node-red npm install node-red-contrib-barcode --save
References
Source Code
https://github.com/yushulx/node-red-contrib-barcode
The post How to Use Node RED with Barcode Module on Windows 10 appeared first on Code Pool.