This one has been working for a long time on Dahua cameras to grab a picture for use on a web site.
Also a nice function if you have a bad line, this command can be used in any known browser also on smartphones.
Latest known firmware for most cameras here in Europe are General_IPC-HX3(2)XXX_Eng_P_V2.212.0001.0.R.20131224
http://IP-adress or hostname:port/cgi-bin/snapshot.cgi
If default http (80) port is used ":port" are not needed
P.S. You can also get live stream in e.g. VLC player with the following string:
The last "subtype=1" mean that subtream from camera are used.
The last "subtype=0" mean that mainstream from camera are used.
rtsp://user:password@IP-adress or hostname:554/cam/realmonitor?channel=1&subtype=1(0)
Coolcruiser