Fixing curl: (56) Recv Failure: Connection Reset by Peer in Your Golang TCP Server

Описание: Learn how to troubleshoot and resolve the `curl: (56) Recv failure: Connection reset by peer` error when hitting a Golang TCP server with this comprehensive guide.
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This video is based on the question https://stackoverflow.com/q/78117345/ asked by the user 'Siddhant K.Singh' ( https://stackoverflow.com/u/11558162/ ) and on the answer https://stackoverflow.com/a/78117397/ provided by the user 'Steffen Ullrich' ( https://stackoverflow.com/u/3081018/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Troubleshooting curl: (56) Recv Failure: Connection Reset by Peer in Golang TCP Server

If you've encountered the curl: (56) Recv failure: Connection reset by peer error while trying to interact with your TCP server in Golang, you're not alone. This error can be frustrating, especially when it seems like everything should be working. In this guide, we'll break down the cause of the issue and provide a clear and concise solution to get your server responding correctly.

The Problem

When you attempt to use the curl command to hit your local server running on Golang, you may receive an error message that says:

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

This error typically indicates that the server has unexpectedly closed the connection while the client (in this case, curl) still had data to send or read. Understanding why this happens is key to resolving the issue.

The Scenario

In the example you provided, the server code successfully starts and listens on port 1729, but it seems to immediately close the connection without processing the incoming HTTP request from curl. Here’s the relevant code snippet:

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

Understanding the Root Cause

The key issue lies in the fact that the server accepts the connection but does not read or process the incoming data. The server is closing the connection directly after accepting it, which results in the curl error. Here's what's happening step-by-step:

Initiating the Connection: When you run curl http://localhost:1729, it sends an HTTP request to the TCP server.

Server Behavior: The server code accepts the connection and then immediately closes without reading any data from the client.

Resulting Error: Since the connection is closed while curl still has data to process, a TCP RST (reset) packet is sent from the server to the client, resulting in the "Connection reset by peer" error.

Solution: Modify Your Server Code

To solve this issue, you need to make the server read from the connection and handle the request properly. Here’s how you can modify the existing code to achieve this:

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

Key Changes Made

Infinite Loop: The server continuously accepts connections, allowing multiple requests to be handled.

Goroutines: Each connection is handled in its own goroutine, enabling simultaneous handling of multiple requests.

Reading the Connection: The server actually reads the data from the connection using ioutil.ReadAll(conn). This ensures the server processes the request instead of closing the connection instantly.

Sending a Response: After reading the request, the server sends a HTTP 200 OK response back to the client, completing the request-response cycle properly.

Conclusion

By modifying your Golang TCP server to read incoming data and respond appropriately, you can resolve the curl: (56) Recv failure: Connection reset by peer error. Understanding the underlying cause of this issue is essential for effective troubleshooting. With these adjustments, your server should now be able to handle requests seamlessly.

If you have further questions or need additional help, feel free to reach out in the comments below!