Скачать или смотреть Resolving PHP file_get_contents Connection Issues on Different Ports

Learn how to solve the problem of PHP's `file_get_contents` sending requests to the same port on IIS 10. Discover practical solutions and insights for server communication issues.
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Resolving PHP file_get_contents Connection Issues on Different Ports

When working with PHP scripts to interact with a server using the file_get_contents function, many developers may encounter unexpected behaviors, particularly when dealing with multiple port requests.

The Problem

A developer experienced an issue when attempting to call different ports on a server running IIS 10 using PHP 7.3.12. Despite changing the port in the script, the requests were consistently logged under the same port, causing confusion during debugging. To illustrate the issue, the script made sequential calls to different ports. However, all requests appeared to point to the initial port used, which was logged repeatedly.

Example of the script that caused confusion:

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

The expectation was for the logs to reflect calls to ports 6447 and 6453 accurately, but they did not.



Understanding the Solution

After thorough investigation, the issue was traced back to the DNS and network configuration. Here's a step-by-step breakdown of how to resolve this problem:

Identify the DNS Configuration:

The PHP scripts were referencing the Fully Qualified Domain Name (FQDN) "example.com".

This DNS entry was being resolved to an internal IP address through a Domain Controller.

Examine the Network Layer:

The IP address was proxying requests through a Citrix Netscaler. This was intended to funnel requests to the correct IIS Server while protecting it from attacks until proper firewall configurations were established.

At the time of the initial setup, everything seemed to work smoothly.

Investigate Why Requests Were Sticking:

It was found that the Netscaler was retaining the connection state, such that subsequent requests from the same source were being directed to the same port. This happened when requests were made too closely together in time.

Implement the Fix:

The key to resolving this issue was altering the internal DNS record for “example.com” so that it pointed directly to the IIS Server’s IP address instead of the Netscaler.

This change ensured that each request was directly routed to the correct port without interference.

Test the Changes:

After updating the DNS settings, the script was rerun, leading to successful logging for each port as intended: 6447 for the first and last calls, and 6453 for the second call.



Conclusion

In cases where PHP scripts do not seem to function as expected when communicating with a server, it’s essential to inspect both the application logic and network settings. As illustrated, a direct connection configuration can alleviate issues caused by intermediary devices such as load balancers or proxies that might cache and not refresh connections properly.

Special thanks to Barmar for assisting in the troubleshooting process—collaboration often leads to quicker resolutions!

By understanding the intricacies of network communication and DNS configuration, you can address similar issues in your development environment efficiently.