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README.jerry.md

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+# D-Modem
+Software modem with **sound**  
+For burble's retro voip modem https://burble.dn42/retro/modem/  
+Now also for JerryXiao's own software voip modems!
+
+Fortunately this old proprietary software modem still works :)
+
+## Prerequisite
+- A desktop GNU/Linux distribution, livecd is also OK
+- See the original README
+- Modem without any sound isn't a real modem? No problem, pulseaudio is used to output modem sound in realtime. You must have pulseaudio dev package installed on your system to compile this software.
+
+## Step-by-step instruction
+
+Execute these commands as a normal user:  
+
+```
+make
+./slmodemd/slmodemd -e ./d-modem
+screen /tmp/ttySL0 115200
+```
+
+Inside the serial console, use the following at commands:  
+
+```
+ATX3
+> OK
+AT+MS=22,1
+> OK
+ATD424026019@voip.burble.dn42
+> CONNECT 1200
+```
+
+You can also connect to:
+| number | AT+MS | ATD | Modulation |
+| ------------ | ------------ | ------------ | ------------ |
+| (42403618)361800 | AT+MS=90,1 | ATD361800@pbx.jerry.dn42 | V.90 |
+| (42403618)361801 | AT+MS=34,1 | ATD361801@pbx.jerry.dn42 | V.34 |
+| (42403618)361802 | AT+MS=34,1 | ATD361802@pbx.jerry.dn42 | V.34 |
+| (42403618)361803 | AT+MS=22,1 | ATD361803@pbx.jerry.dn42 | V.22 |
+| (42403618)361804 | AT+MS=22,1 | ATD361804@pbx.jerry.dn42 | V.22 |
+| (42403618)361805 | AT+MS=23,1 | ATD361805@pbx.jerry.dn42 | V.23 |
+| (42403618)361806 | AT+MS=23,1 | ATD361806@pbx.jerry.dn42 | V.23 |
+
+Now you should be connected. If you see a login prompt, go to https://burble.dn42/retro/modem/ for login username and password. Once logged in, close out of GUN Screen and execute pppd like this:  
+
+```
+sudo pppd $(readlink /tmp/ttySL0) 1200 user dn42 noauth nodefaultroute nodetach
+```
+
+nodefaultroute is used here to keep your voip alive :)  
+
+## netns
+If you would like a full dialup dn42 experience, try using netns:  
+
+```
+sudo ip netns add modem
+sudo ip netns exec modem pppd $(readlink /tmp/ttySL0) 1200 noauth nodefaultroute nodetach
+```
+
+Start a new terminal and  
+```
+sudo ip netns exec modem $SHELL
+unshare -m
+echo 172.23.0.53 > /tmp/resolv.conf
+mount --bind /tmp/resolv.conf /etc/resolv.conf
+ping burble.dn42
+```
+
+Have fun!
+
+
+## Server
+This code can also work as a server, no docs available though ;)  
+Just type ATA in the modem console and try it out first.