Cellular Network Infrastructure

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h1. Simple Echo Test Setup for your OsmoCom CNI

Some people want to test the audio setup of their OsmoCom Network with just one phone, by calling a number that will echo back the audio stream.

Even though it is quite some overkill, It turns out that probably the simplest setup for such a thing is using *SEMS, the SIP Express Media Server* .

SEMS is not included with most Linux distributions, Alpine Linux being an exception (https://pkgs.alpinelinux.org/packages?name=sems) but there are a number of projects that maintain binary repositories. Of course, you can build it yourself, there are a number of forks, all hosted publicly on infrastructure that this author prefers not to link to, so you will have to search it. Anyway, such things as URLs can quickly go out of date and I do not intend to maintain this page with links to current repositories of source or binary packages.

For the purposes of this tutorial, lets pull SEMS package from the repo maintained by folks at sipwise, If this information, written in November 2022, is out of date, then you will have to search for a more current solution.

Run (as root):

<pre>

echo "deb [arch=amd64] https://deb.sipwise.com/spce/mr10.2.1/ bullseye main" > /etc/apt/sources.list.d/sipwise.list

cd /tmp

wget https://deb.sipwise.com/spce/keyring/ngcp-archive-keyring_mr10.2.1.deb

dpkg -i ./ngcp-archive-keyring_mr10.2.1.deb

apt update

apt install ngcp-sems

</pre>