Resolving the Client-Server Communication Issue: Why Is the Response from the Server Not Received?

Discover why your client isn't receiving responses from the server in your JavaScript and Go application, and learn how to resolve CORS issues effectively.
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Understanding the Client-Server Communication Problem

In the world of web development, creating a simple client-server application can be an exhilarating yet challenging journey. If you're using JavaScript for the client-side and Go for the server-side, you may have stumbled upon a common issue: the client not receiving the response message from the server.

Imagine this scenario: you have your server running fine, but as you click a button on the client-side, instead of the expected message, you see the raw HTML code being returned. This can be perplexing, particularly for someone who is just starting with client-server applications. In this guide, we'll dive deep into understanding this problem and how to solve it effectively.

The Core of the Issue

When working with web applications, one of the critical concepts to understand is CORS (Cross-Origin Resource Sharing). If the server and client are being executed on different ports, the browser applies CORS policies to restrict resources from being requested from other origins. This is likely the reason for the unexpected behavior you're observing.

What Happened?

You clicked the button on your web page.

The fetch request was made to the server.

However, the server's response was not what you expected (you received HTML instead of your server's intended message).

The Solution: Adjusting CORS in Your Go Server Code

One common solution to this CORS related issue is to adjust how the server communicates its permissions for cross-origin requests. Here’s how you can fix it.

Modify the Go Server Code

Original Code

Your Go handler code likely looks something like this:

[[See Video to Reveal this Text or Code Snippet]]

Suggested Change

Instead of limiting access to just one port, you should modify your header in the handler function to allow requests from all origins:

[[See Video to Reveal this Text or Code Snippet]]

Explanation of the Change

By using *, you inform the server that it should accept requests from any origin. This is particularly useful during development when you may have multiple ports in use, making it easier to test your application.

Checking Your Ports

Server Port: Ensure your Go server is running on port 5500.

Outcome

After making this change, the CORS error should disappear. You should be able to successfully retrieve the server's message when you click the button on your client-side application.

Final Thoughts

Understanding how the browser security model works is crucial in web development, particularly when dealing with client-server architecture. CORS issues can be a roadblock for many developers, but with a few adjustments, you can overcome them.

Don't hesitate to keep experimenting with your application. Every problem you encounter is an opportunity to learn and grow as a developer!

If you have any questions or comments, feel free to reach out!