This is a try to simulate basic VLR SGs procedures for MME.
In case you don't have VLR but need to test your MME installation for voice centric UEs and CS Fallback - this is your friend.
The program accepts SCTP connection from MME and answers four basic SGs messages initiated by MME:

• Location Update request
• EPS detach indication
• IMSI detach indication
• MME failure

Other messages are silently ignored.

Run:
vlr.py <ip> <port>

<ip> - IP address to listen to
<port> - TCP port to listen to. SGsAP default port is 29118

SIGUSR1 dumps SGs statistics of the running process

Run it manually or add to the systemd services:

$ cat /etc/systemd/system/vlr.service
[Unit]
Description=lab VLR simulator to fool MME over SGs
After=network.target
StartLimitIntervalSec=0
[Service]
Type=simple
Restart=always
RestartSec=10
User=user
ExecStart=/home/user/SGsAP/vlr.py 10.0.0.29 29118

[Install]
WantedBy=multi-user.target

Configure VLR 10.0.0.29:29118 on your MME for CS Fallback simulation