Internet Control Message Protocol  

The Internet Control Message Protocol (ICMP) control enables your application to send and receive ICMP echo datagrams. These are a special type of IP datagram which can be used to determine if a server is reachable, as well as determine the amount of time it takes for data to be exchanged with the local system. The ICMP control can also be used to trace the route that data takes from the local system to the server, which can be useful in determining why a connection to a particular system may be experiencing higher latency than normal.

The following properties, methods and events are available for use by your application:

Initialize the control and validate the runtime license key for the current process. This method is normally not used if the control is placed on a form in languages such as Visual Basic. However, if the control is being created dynamically using a function similar to CreateObject, then the application must call this method to initialize the component before setting any properties or calling any other methods in the control.

Unload the Windows Sockets library and release any resources that have been allocated for the current process. This is the last method call that the application should make prior to terminating. This is only necessary if the application has previously called the Initialize method.

Ping and TraceRoute

To determine if a server is reachable, your application can send ICMP echo datagrams. You can also map the route between the local system and the server by sending a series of echo datagrams to each intermediate host. This is what the ping.exe and tracert.exe command line utilities do, and you can emulate that functionality in your own applications.

This is the simplest method you can use to send ICMP echo datagrams. Specify the server, the size of the ICMP datagram you want to send and the number of times you want to send it. The method will return if the operation was successful along with information such as the average number of milliseconds it took for the datagram to be returned by the server.

This method will map the route that data packets take from your local system to a server. Whenever you send data over the Internet, that data is routed from one computer system to another until it reaches its destination. This method returns statistical information about each system that the data is routed through, and the latency between that system and the local host. For each intermediate host in the route to the destination server, the OnTrace event will fire.

This event is generated when the TraceRoute method is called. The event will fire for each intermediate host in the route from the local system and the server.