It depends on whether the Internet provider has prioritised incoming traffic only or in both directions on port 8080. For example, the Ziggo ISP only delivered slightly better uplink performance over port 8080, which means a home server operating on port 8080 would probably only deliver a small improvement.
On the other hand, one way to exploit the extra bandwidth would be to make a VPN connection over port 8080 to a nearby server (e.g. privacy VPN that supports connections over 8080). Last year when the Three mobile network here had something like a 10x speed variation between HTTP and HTTPS, I use to connect to a VPN to get much faster Internet access on my mobile. Now their network has got so congested that the high latency degrades the VPN performance.
I'll do some further checking, but from a first glance their test is very customisable which is nice, i.e. you can select the number of threads to use, whether to run over http or https, limit data usage (for metered ISPs), select a server location and various other settings.
By default, DSLReports runs its test multithreaded (multiple connections to test server) and according to TCPView, it does this over the http on the downlink going by TCPView, which is also nice. So without changing any settings, it aims to measure your ISP's maximum throughput and using port 80 for the download (not 8080). This is similar to downloading a large Linux ISO using a download accelerator that downloads multiple parts of the file simultaneously. On the other hand, it runs its uplink over port 8888 for some reason, but at least it's different to what speedtest.net uses.
In the settings page, there is an option to specify how many streams (their word for threads) to run over, so you can select '1' for the download and upload to run a test similar to how TestMy runs by default, i.e. like the bandwidth you get from streaming video or downloading a single large file in your web browser.
TestMy can run a Multithread test also as mentioned on page #6, however, it doesn't provide the ability to specify how many threads to use. By default, it runs its test over a single connection to the test server.
Basically the main point of this article is to show that some ISPs are giving priority to traffic on port 8080 to inflate the speedtest.net figures. However, as TestMy has support for running its tests over both port 80 (http) and port 8080, I used it for the demonstrations in this article.
I also prefer TestMy over Ookla's Speedtest due to its ability to test with a single connection, particularly with wireless ISPs that are quite common in Ireland. Some of these ISPs deliver very little bandwidth over a single connection (e.g. 4Mbps) even to a nearby server, probably to prevent YouTube and streaming services going into 1080p mode. However, if one tests the same ISP with Speedtest.net, it will give the impression that there's plenty of bandwidth for 1080p video since Speedtest tests over multiple simultaneous connections to its test server.