Tutorials 4 min read

Troubleshooting WebSocket Connection Failed: A Concise Guide

WebSocket connection failure is a common issue in web development. This article provides insights into the reasons behind WebSocket connection failures and offers practical solutions to help you quickly resolve the problem.

Troubleshooting WebSocket Connection Failed: A Concise Guide

In modern web applications, WebSocket has become a popular technology for real-time communication. It enables data exchange between clients and servers over a single TCP connection. It is part of HTML5 and is widely supported by modern web browsers, including Chrome, Firefox, Safari, and Edge.

WebSocket connection failure is a common issue in web development. This article provides insights into the reasons behind WebSocket connection failures and offers practical solutions to help you quickly resolve the problem.


Common Reasons for WebSocket Connection Failures

However, there are instances where WebSocket connections fail to establish successfully, leading to interrupted data transmission and compromised functionality. Here are some common reasons for WebSocket connection failures and their corresponding solutions:

Network Issues:

Check if your network connection is functioning properly, ensuring that your device has internet access.

Make sure that firewalls or proxy servers are not blocking WebSocket connections. Try connecting using different network environments or devices to rule out any network configuration issues.

Server Issues:

Ensure that the WebSocket server is running and listening on the correct port. Check the server's log files for any error messages or warnings. Reach out to the server administrator or development team for more information about server configuration and status.

Protocol Mismatch:

Verify that the WebSocket protocol version used by both the client and server is consistent. Confirm that your application is compatible with the latest specifications of the WebSocket protocol.

Security Concerns:

Check if your website or application is using the HTTPS protocol. Some browsers require WebSocket connections to be established only over encrypted connections. Validate the validity of your SSL certificate and ensure it matches your domain.

Coding Errors:

Inspect your JavaScript code for syntax errors related to WebSocket. Ensure that you correctly instantiate the WebSocket object and use the appropriate URL for the connection.

Cross-Origin Issues:

Verify if your WebSocket requests are restricted by cross-origin policies. WebSocket connections require appropriate Cross-Origin Resource Sharing (CORS) header information set on the server.

Resource Limitations:

Check server resource limitations to ensure it can handle and maintain a large number of WebSocket connections. Consider implementing load balancing and clustering techniques to handle high-concurrency WebSocket connection requests.

How to Fix WebSocket Connection Failed (Nginx Server)

WebSocket Connection Failed

Have you also encountered the WebSocket Connection Failed situation mentioned above? In most cases, a 400 error is caused by a reverse proxy. Are you using Nginx?

'WebSocket connection failed' typically indicates an issue with the WebSocket configuration of the Nginx server. Correctly configuring the server to support WebSocket can resolve this problem.


Step 1: Check if your Nginx version supports WebSocket. If your version is 1.3 or higher, WebSocket is supported.

Step 2: Edit your Nginx configuration file. You should locate the following line of configuration within the server block of the nginx.conf file.

location / {
    # ...

Step 3: Add the following configuration lines to enable WebSocket support:

  • proxy_pass to send WebSocket traffic to the proxy server (with upstream being the target URL).
  • proxy_http_version to set the request protocol version to 1.1.
  • Set the value of the Upgrade header to $http_upgrade, which is the value of the request header with the 'Upgrade' title.
  • Set the value of the Connection header to 'upgrade' to indicate a successful upgrade of the connection.
location / {
    proxy_pass http://your_upstream;
    proxy_http_version 1.1;
    proxy_set_header Upgrade $http_upgrade;
    proxy_set_header Connection "upgrade";
    proxy_read_timeout 86400;

Step 4: Save and exit the configuration file, then restart the Nginx service to apply the changes.

Step 5: Verify that you have correctly configured the Nginx WebSocket settings. You can use the following command to check if Nginx is configured to support WebSocket.

$ nginx -t

Step 6: If the command displays "OK," WebSocket is configured correctly. If the command shows an error, please review and fix your configuration file accordingly.

How to Debug WebSocket Service with Apidog

If you are developing a WebSocket service and need to debug it, we recommend using some excellent API debugging tools like Apidog. This tool is perfect for debugging WebSocket services. Google Chrome Extension Apidog has both a web version and a client version. If you are using the web version and want to debug a local service, you need to install the Apidog Chrome extension.

Apidog Google Chrome extension

Download link: Apidog Google Chrome extension.

To initiate a WebSocket connection, follow these steps in Apidog:

1. Click on the "+" button.

2. Enter the address of the WebSocket service.

Optionally, fill in the "Message" and "Params" fields to provide additional information.

Setting Message and Params

3. Save the request for future use by clicking the "Save" button.

4. Connect and Send WebSocket Request

5. Click the "Connect" button to establish a WebSocket connection with the server.

Once connected, you can send messages to the server using the "Send" button in Apidog.

6. To disconnect from the WebSocket service, click the "Disconnect" button.


In summary, troubleshooting WebSocket connection failures is vital for maintaining smooth and uninterrupted communication between clients and servers in web development.

By identifying the common causes of these failures and implementing effective solutions, such as resolving Nginx server configuration issues and utilizing debugging tools like Apidog, developers can ensure the reliable operation of WebSocket services. By following best practices and addressing any connection issues promptly, developers can optimize the performance and functionality of WebSocket-enabled applications.

Join Apidog's Newsletter

Subscribe to stay updated and receive the latest viewpoints anytime.