Accessing a RTSP cam stream from a remote site with opencv, requires two basic computers, e.g. rpi3s, one in each LAN.
A serial vpn link is setup between the two rpis with the following commands on the remote rpi.
Install ppp package on both the rpis:
sudo apt update
sudo apt upgrade
sudo apt install ppp
Check IP forwarding is enabled on both the rpis:
sysctl net.ipv4.ip_forward
net.ipv4.ip_forward = 1
If the value is '0' then:
edit /etc/sysctl.conf. Search for a line containing the entry #net.ipv4.ip_forward=1, and remove the # at the beginning of the line. Save the file and run the sysctl command to enable the edited setting:
sudo sysctl -p /etc/sysctl.conf
vpn-s
#/bin/bash
# vpn-s script sets up a point-to-point vpn between remote computer
# and local computer on the home LAN.
# Run this script on the remote computer. Tested on Raspbian and Debian10.
sudo /usr/sbin/pppd updetach connect-delay 60000 noauth pty\
"sudo -u usrname_remote /usr/bin/ssh -t -t usrname@home_router_ip -p home_router_port_no_fwd_to_rpi\
sudo /usr/sbin/pppd noauth 192.168.186.2:192.168.186.1"
fwdonremote
#!/bin/bash
# Edit in below your actual local, i.e. home, LAN address (as provided by ISP).
#start ssh vpn first (vpn-s) then run this script on remote computer.
sudo iptables -F
sudo iptables -t nat -F
sudo ip r add 192.168.1.0/24 dev ppp0
sudo iptables -t nat -A POSTROUTING -o wlan0 -j MASQUERADE
fwdonlocal
#!/bin/bash
# Edit in below your actual remote LAN address (as provided by ISP).
#After ssh vpn has been established by remote run this script here on
#the local computer.
sudo iptables -F
sudo iptables -t nat -F
sudo ip route add 192.168.0.0/24 dev ppp0
sudo iptables -t nat -A POSTROUTING -o wlan0 -j MASQUERADE
Install the following python packages if not previously installed on remote rpi.
pip install --upgrade pip
pip install numpy
pip install opencv-python
Running open_uri.py with your own camera rtsp://url edited in should connect to the ipcam on home LAN and open a display window in the remote rpi.
Note: If remote rpi is running in headless mode, connection to it should be made with X forwarding enabled to access the display say with ssh -XY rpi3-remote.
vpn-s requires the ssh login from remote rpi to local rpi is passwordless with no keyboard interaction. The sudo command on both the rpis is also passwordless with no keyboard interacion.
fwdon scripts require the iptables on both the rpis are in their default setting before use, which can be set as:
sudo iptables -F
sudo -t nat -F
Check if your rpis have ufw, check if it's active. If so, it may be blocking network traffic in some way.