Here is how to enable Telnet on my Hikvision NVR using a cURL command, you can use it on the camera's as well.
cURL Command:
curl -T telnet_on.xml http://admin:12345@192.168.1.100:80/ISAPI/System/Network/telnetd
curl -T telnet_off.xml http://admin:12345@192.168.1.100:80/ISAPI/System/Network/telnetd
Contents of telnet_on.xml:
<?xml version="1.0" encoding="UTF-8"?>
<Telnetd version="2.0" xmlns="http://www.isapi.org/ver20/XMLSchema">
<enabled>true</enabled>
</Telnetd>
Contents of telnet_off.xml:
<?xml version="1.0" encoding="UTF-8"?>
<Telnetd version="2.0" xmlns="http://www.isapi.org/ver20/XMLSchema">
<enabled>false</enabled>
</Telnetd>
cURL Command:
curl -T telnet_on.xml http://admin:12345@192.168.1.100:80/ISAPI/System/Network/telnetd
curl -T telnet_off.xml http://admin:12345@192.168.1.100:80/ISAPI/System/Network/telnetd
Contents of telnet_on.xml:
<?xml version="1.0" encoding="UTF-8"?>
<Telnetd version="2.0" xmlns="http://www.isapi.org/ver20/XMLSchema">
<enabled>true</enabled>
</Telnetd>
Contents of telnet_off.xml:
<?xml version="1.0" encoding="UTF-8"?>
<Telnetd version="2.0" xmlns="http://www.isapi.org/ver20/XMLSchema">
<enabled>false</enabled>
</Telnetd>