How to send/write and receive/read (BIDI) Bluetooth Data from Javascript

---

Product JSPrintManager Published 06/01/2023 Updated 11/05/2026 Author Neodynamic

---

Overview

JSPrintManager supports Bidirectional (BIDI) Bluetooth Communication through the RFCOMM (Radio frequency communication) protocol from Javascript allowing you to Send/Write & Receive/Read data strings to any BT Address and Channel reachable from the client system. Based on pure Javascript code, you can enable BIDI Bluetooth Comm on any web page (written on top of any Web Platform including ASP.NET MVC/CORE, PHP, Django, Ruby On Rails (RoR), Express.js, Angular, React, Vue).

In this walkthrough, you'll learn how to Send/Write & Receive/Read data strings from Javascript through any BT Address and Channel reachable from the client machine. This solution works with any popular browser like Chrome, Edge, Firefox & Safari on Windows, Linux, Raspberry Pi, Android and Mac systems!

Step-by-step

• JSPrintManager Client App

  Be sure you install in your dev machine JSPrintManager (JSPM) (Available for Windows, Linux, Raspberry Pi, Android & Mac)
  
  
  IMPORTANT: This small app must be installed on each client!
  Since Chrome 142, browsers ask the user to allow Local Network Access the first time your website connects to the JSPrintManager App.

• HTML & Script References

  • Download JSPrintManager.js
  • Copy all of these *.js files to the same folder where the next index.html page sample will be located in.
  • By using your favorite Web Development IDE or Text Editor, create a new HTML file naming it index.html
    Copy/paste the following code inside that html file:
    
    

    
    <!DOCTYPE html>
    <html>
    <head>
        <title>JSPrintManager</title>
        <meta charset="utf-8" />
    </head>
    <body>
        <div style="text-align:center">
            <h1>BIDI Bluetooth Comm from Javascript</h1>
            <hr />
            <label>Paired Bluetooth devices: <select id="btDevices" onchange="document.getElementById('btAddress').value = this.value;"></select></label>
            <label>Address: <input id="btAddress" placeholder="00:00:00:00:00:00" /></label>
            <label>Channel: <input id="btChannel" value="1" /></label>
            <p><small>IMPORTANT: The target Bluetooth address must be in the client's allow list!</small></p>
            <br /><br />
            <button type="button" onclick="doOpen();">Connect</button>
            <button type="button" onclick="doClose();">Close</button>
            <hr />
            <strong>Data to send</strong>
            <input id="txtDataToSend" placeholder="Type data here..." />
            <button type="button" onclick="doSendData();">Send...</button>
            <hr />
            <textarea id="txtDataReceived" readonly style="background-color:#302a2a;color:#fff;font-family: 'Courier New', Courier, monospace;" cols="100" rows="10"></textarea>
        </div>
    
        <!-- JSPrintManager.js (download it or install it with: npm install jsprintmanager) -->
        <script src="JSPrintManager.js"></script>
        <script>
            var comm = null;
    
            // Start the connection with the JSPrintManager Client App
            JSPM.JSPrintManager.auto_reconnect = true;
            JSPM.JSPrintManager.start();
            JSPM.JSPrintManager.WS.onStatusChanged = function () {
                if (jspmWSStatus()) {
                    // get the client Bluetooth devices
                    JSPM.JSPrintManager.getBluetoothDevices().then(function (btDevicesList) {
                        var select = document.getElementById('btDevices');
                        select.innerHTML = '';
                        for (var i = 0; i < btDevicesList.length; i++) {
                            select.add(new Option(btDevicesList[i].name + ' (' + btDevicesList[i].address + ')', btDevicesList[i].address));
                        }
                        if (btDevicesList.length > 0) document.getElementById('btAddress').value = btDevicesList[0].address;
                    });
                }
            };
    
            // Open the connection with the device
            function doOpen() {
                if (!jspmWSStatus()) return;
                comm = new JSPM.BTComm(val('btAddress'), parseInt(val('btChannel')));
                comm.onDataReceived = function (data) {
                    log("< " + data);
                };
                comm.onError = function (data, isCritical) {
                    log("ERROR: " + data);
                };
                comm.onClose = function (data) {
                    log("COMM CLOSED!");
                    comm = null;
                };
                comm.connect().then(function () {
                    log("BT COMM CONNECTED!");
                });
            }
    
            // Send data to the device
            function doSendData() {
                if (!comm) {
                    log("The connection is not open!");
                } else if (val('txtDataToSend').length > 0) {
                    comm.send(val('txtDataToSend'));
                    log("> " + val('txtDataToSend'));
                }
            }
    
            // Close the connection
            function doClose() {
                if (comm) comm.close();
                else log("The connection is not open!");
            }
    
            // Write a line in the data received box
            function log(text) {
                console.info(text);
                document.getElementById('txtDataReceived').value += text + "\r\n";
            }
    
            // Check the connection status with the JSPrintManager Client App
            function jspmWSStatus() {
                var status = JSPM.JSPrintManager.websocket_status;
                if (status == JSPM.WSStatus.Open) {
                    return true;
                } else if (status == JSPM.WSStatus.WaitingForUserResponse) {
                    console.info('Waiting for the user to allow this website (JSPrintManager dialog or browser Local Network Access prompt)...');
                } else if (status == JSPM.WSStatus.Blocked) {
                    alert('JSPrintManager has blocked this website!');
                } else if (status == JSPM.WSStatus.NotInstalled || status == JSPM.WSStatus.Closed) {
                    alert('JSPrintManager Client App is not installed or not running! Download it from https://neodynamic.com/downloads/jspm');
                } else if (status == JSPM.WSStatus.CertificateError) {
                    alert('A TLS/SSL certificate error prevented the connection with JSPrintManager Client App.');
                } else if (status == JSPM.WSStatus.ConnectionError) {
                    alert('A network error (e.g. a firewall) prevented the connection with JSPrintManager Client App.');
                }
                return false;
            }
    
            // Helpers
            function val(id) { return document.getElementById(id).value; }
            function checked(id) { return document.getElementById(id).checked; }
    
            // Fill a <select> element with a list of items
            function fillSelect(id, items, getText) {
                var select = document.getElementById(id);
                select.innerHTML = '';
                for (var i = 0; i < items.length; i++) {
                    var text = getText ? getText(items[i]) : items[i];
                    select.add(new Option(text, text));
                }
            }
        </script>
    </body>
    </html>
    

  
  
• That's it! Run your website and test it.

Try JSPrintManager Online Demo!