If you want to Edit an existing, or create a new Monitor, rightclick on a Machine -> Edit -> Monitors and you will see a form similar to the one shown below in Figure 1:
Figure 1: Default Monitors
You can add a new Monitor by clicking on the Add button. Once you click on Add button, the following screen opens up:
Figure 2: Add Monitor
Which type of Monitor would you like to add?
There are four types of Monitors that you can add, these are shown in the figure below:
Figure 3: Types of Monitors
Ping Monitor
The PING Monitor uses the ICMP Protocol to send a ICMP_Echo to the configured host.
TCP Monitor
Use this monitor if you want to monitor TCP based Services like POP3, FTP or NNTP.
HTTP Monitor
The HTTP Monitor is specialized for HTTP based Services. It is based on the TCP Service, and additionally use the http protocol to query the webserver.
UDP Monitor
UDP Services are usually very difficult to monitor due the nature of the UDP Protocol. However there are many services, specially gameservers, who respond on UDP requests and so can be monitored.