Скачать или смотреть How to Fix the 404 Not Found Error When Using Sockets in Python 3

Learn how to resolve the `404 Not Found` error while working with socket programming in Python 3. This guide breaks down common mistakes and provides solutions for sending valid HTTP requests.
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Understanding the 404 Not Found Error in Python Socket Programming

If you are delving into socket programming with Python, you might encounter errors that can be quite perplexing, particularly the 404 Not Found error. This issue typically arises when the HTTP request being sent does not conform to the expected format, leading the server to not find the requested resource. In this guide, we will explore a sample Python code that triggers this error and guide you on how to correct it.

The Problem

Consider the following code snippet, which attempts to retrieve a file using Python's socket library:

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

Upon running this code, you might see the following error returned by the server:

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

Despite using the socket library correctly, the error indicates that the server cannot find the requested resource. Interestingly, if you use the urllib library to make the same request, it works perfectly. This discrepancy raises a critical question: What are we doing wrong with the socket request?

The Solution

The problem primarily lies in the way the HTTP request is composed. To send a valid HTTP request through TCP sockets, you must follow specific formatting rules.

Key Mistakes in the Request:

Using Absolute URL Instead of Path:
The request sent must contain only the path to the resource, not the full URL.

Missing Host Header:
While an HTTP/1.0 request might not strictly require a Host header, it is good practice to include it, especially since many servers expect it.

Incorrect Line Endings:
The HTTP protocol specifies that line endings should be \r\n, not just \n. Using the wrong line endings can cause the server to misinterpret the request.

Correcting the Request

Here’s how to revise the HTTP request to be valid:

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

Step-By-Step Explanation:

The Method: GET specifies the type of HTTP request we're making.

The Path: /code/romeo.txt is the correct path to the resource you want to access on the server.

HTTP Version: HTTP/1.0 indicates the version of HTTP being used for the request.

Host Header: Host: www.py4inf.com explicitly tells the server which host is being accessed.

Proper Line Endings: Use \r\n to denote the end of the line and to separate headers.

Conclusion

In conclusion, while working with sockets in Python, it's crucial to format your HTTP requests correctly to avoid common pitfalls like the 404 Not Found error. Always catch these key aspects: use the correct path, include a Host header, and ensure your line endings are compliant with the HTTP protocol.

With these adjustments, your socket programming experience in Python will be smoother and more effective. Happy coding!