tct

tct (tcp connection timer) is a quick and minimal program (< 70 LoC!) that helps determine the "optimal" number of parallel TCP requests for your network connection.

It performs a series of tests (following your desired configuration) by incrementally increasing the number of parallel requests and measuring the time taken for each test.

The optimal number is identified as the point where adding more parallel requests does not significantly reduce the overall time taken.

Motivation

The Nix Package Manager has an option called http-connections that, as per the wiki, sets the "maximum number of parallel TCP connections used to fetch files from binary caches and by other downloads."

I have found this option a little obscure, however, as the default value (25) has no solid motivation behind it. Is it optimal? I don't know. Can it be optimized? Probably. tcp has been designed to help you decide a loose range to set http-connections in.

Do keep in mind that this is not 100% accurate. There are many factors that may affect the results of network related tests.

Usage

tct -url="http://yourtargeturl.com" -max=200 -delay=500ms

Replace "http://yourtargeturl.com" with the actual URL you wish to test against. You can also omit the URL and use an IP address instead, for example, 8.8.8.8 for Google or 1.1.1.1 for Cloudflare. You may notice differences between target URLs.

The -max parameter specifies the maximum number of parallel requests to test, and -delay sets the interval between each request.

Note

You are strongly advised to use the delay option. I have observed high latency while running with the default 0 second delay, which is likely some form of throttling by the host. If you test against an URL that you know does not throttle connections, then you may consider omitting -delay.

Flags

• -url: The URL to fetch.
• -max: Maximum number of parallel requests to test. Default is 100
• -delay: Delay between requests. Can be specified as a duration (e.g., 500ms). Default is 0 (i.e. no delay)

Notes

• Remember to adjust the -max and -delay parameters based on your network conditions and the capabilities of the target server. tct tries not to make any assumptions, but the default values will not be suitable for all testing conditions.
• tct will try to always exit gracefully when you, e.g., kill the program with ctrl+c.

Contributing

Contributions are always welcome. If you have any suggestions, create an issue. If you would like to fix my code (can't blame your for it) then create a Pull Request.

Reference

• Implementing graceful shutdown in go