iperf3 -c 127.0.0.1 -i1 -t 9999 -b50M -u -p5003 -d -P2 -V failed

[zyp2015]

NOTE: The iperf3 issue tracker is for registering bugs, enhancement
requests, or submissions of code. It is not a means for asking
questions about building or using iperf3. Those are best directed
towards the iperf3 mailing list at [email protected] or
question sites such as Stack Overflow
(http://www.stackoverflow.com/). A list of frequently-asked questions
regarding iperf3 can be found at http://software.es.net/iperf/faq.html.

Context

• Version of iperf3: https://iperf.fr/iperf-download.php iPerf 3.0.11

• Hardware: i7 8700

• Operating system (and distribution, if any): Windows 10

Please note: iperf3 is supported on Linux, FreeBSD, and macOS.
Support may be provided on a best-effort basis to other UNIX-like
platforms. We cannot provide support for building and/or running
iperf3 on Windows, iOS, or Android.

• Other relevant information (for example, non-default compilers,
  libraries, cross-compiling, etc.):

Please fill out one of the "Bug Report" or "Enhancement Request"
sections, as appropriate.

Bug Report

iperf3 -s -p5003 -i1 -d -V
iperf 3.0.11
send_parameters:
{
"udp": true,
"omit": 0,
"time": 9999,
"parallel": 2,
"len": 8192,
"bandwidth": 50000000
}
Time: Thu, 10 Jun 2021 11:41:07 GMT
Connecting to host 127.0.0.1, port 5003
Cookie: P80275846.1623325266.990841.454af7bc
[ 4] local 127.0.0.1 port 50142 connected to 127.0.0.1 port 5003
iperf3 -c 127.0.0.1 -i1 -t 9999 -b50M -u -p5003 -d -P2 -V
iperf 3.0.11
send_parameters:
{
"udp": true,
"omit": 0,
"time": 9999,
"parallel": 2,
"len": 8192,
"bandwidth": 50000000
}
Time: Thu, 10 Jun 2021 11:41:07 GMT
Connecting to host 127.0.0.1, port 5003
Cookie: P80275846.1623325266.990841.454af7bc
[ 4] local 127.0.0.1 port 50142 connected to 127.0.0.1 port 5003

Doesn't it seem that UDP does not support multi-threading?

[zyp2015]

I use the latest code and compile with cygwin+gcc. This problem also exists. Is this caused by the Windows platform?

[davidBar-On]

This seem to be a known issue. See issue #472 and especially this note.

[zyp2015]

This seem to be a known issue. See issue #472 and especially this note.

Ok thank you very much, i will check it out

[davidBar-On]

Submitted PR #1163 with a fix for the issue, based on the approach taken by @rossro in issue #472. It will help if you will test the change. Note that when Cygwin is used the change requires to specify the number of ports available for the parallel streams in the -p parameter.