Tips for Debugging and Troubleshooting HTTP Status Codes

Master the debugging and troubleshooting skills of HTTP status codes

When using web applications, we often encounter various HTTP status codes. These status codes are standardized codes returned by the server when responding to requests to tell the client the processing results of the request. Understanding and mastering the meaning of HTTP status codes can help us better debug and troubleshoot problems in applications.

This article will introduce some common HTTP status codes and corresponding debugging and troubleshooting techniques to help readers quickly solve common web application problems.

1. 1xx series status codes (informational status codes)

This series of status codes indicates that the server has received the request and is processing it. Common 1xx status codes are:

• 100 Continue: Indicates that the server has received part of the request and is ready to continue processing the request. You can observe whether the request is processed normally during debugging.
• 101 Switching Protocols: Indicates that the server is switching protocols or upgrading protocols. This status code is relatively common in applications such as WebSocket.

Debugging tips: Use network packet capture tools (such as Wireshark) or browser developer tools to view the detailed information of HTTP requests and responses. Observe whether there are multiple switching processes between requests and responses.

2. 2xx series status codes (success status codes)

This series of status codes indicates that the request has been successfully processed. Common 2xx status codes are:

• 200 OK: Indicates that the request has been successfully processed and the corresponding result is returned. This is one of the most common success status codes.
• 201 Created: Indicates that the request has successfully created a new resource. You can observe the URL of the new resource or other information related to successful creation during the debugging process.

Debugging tips: Check the returned response content to see if it meets expectations. If the request is to create a resource, you can confirm whether the new resource was successfully created.

3. 3xx series status codes (redirect status codes)

This series of status codes indicates that the client needs to take further action to complete the request. Common 3xx status codes are:

• 301 Moved Permanently: Indicates that the requested URL has been permanently moved to a new location. The new redirect URL can be observed during debugging.
• 302 Found: Indicates that the requested URL has been temporarily moved to a new location. Similar to the 301 status code, but represents a temporary redirect.

Debugging tips: Check the Location field in the returned response header to see if there is a new URL address. You can check the browser's network request records to find redirect links and confirm that the request and response are proceeding as expected.

4. 4xx series status codes (client error status codes)

This series of status codes indicates that there is an error in the request sent by the client. Common 4xx status codes are:

• 400 Bad Request: Indicates that the request has a syntax error and the server cannot understand it.
• 404 Not Found: Indicates that the requested resource does not exist. This is one of the most common client error status codes.

Debugging tips: Check whether the request parameters and URL address are correct, and ensure that the requested resource actually exists. You can view the server's log files to further analyze the cause of the problem.

5. 5xx series status codes (server error status codes)

This series of status codes indicates that an error occurred when the server processed the request. Common 5xx status codes are:

• 500 Internal Server Error: Indicates an internal server error. This is one of the most common server error status codes.
• 503 Service Unavailable: Indicates that the server is currently unable to process the request, usually because the server is overloaded or under maintenance.

Debugging tips: Check the server's error log to see if there are any exceptions or error messages. You can add log output to troubleshoot problems.

HTTP status codes are important guidelines and clues when debugging and troubleshooting web application problems. By understanding these common status codes and corresponding debugging and troubleshooting skills, we can more quickly locate the cause of the problem and take appropriate measures to solve the problem in a timely manner. Mastering the debugging and troubleshooting skills of HTTP status codes is a very important skill for web development and operation and maintenance personnel.

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