Net Tool Box - The Ultimate Mac Networking Utility


| About | Features | Order | Support

Pinger

What does it do?

Pinger is a very simple implementation of the ICMP (Internet Control Message Protocol) protocol. It allows you to test connectivity and response times across a network or the Internet.

How does it work?

Pinger sends a small string of data to a target host a set number of times at a set interval. It will then count the time it takes for that packet to return from the target and if it takes longer than a set timeout value, it is discarded.

How do I use it?

Note: Because ICMP sockets can only be opened by root-processes, you can only use the "legacy" ping tool (shown on the left) when authenticated. If you aren't authenticated, you will only be able to use the text-based ping tool. See Using Net Tool Box for more information on authentication.

In Net Tool Box, click the "Pinger" button on the toolbar. When the Ping window appears, type the DNS name or IP address of the target in the "Target" field. If you want to change the number of times the host is pinged, change the "Count" field to your preferred value. Also, if you know your network is particularly slow or fast, change the "Timeout" value as required. Also, if you want to increase or decrease the interval between pings, change the "Interval" field.
Once you have set the values press "Start". Pinger will then start sending the packets. When a packet has been sent a row will be added to the list with the packet number in the second column. Once a packet has been received, it will display a tick in the "Received" column and the time it took (in milliseconds) in the "Time" column. If a packet has not been received in less than the timeout value, it will be marked with a "X" in the "Received" column.
If you are using the textual-based ping tool, the results will not be shown in the same way. They will appear as text with each line describing the state in which each packet was received. One benefit of the textual ping tool is that it allows you to ping your subnet for responses (instead of one machine). To do this you should try entering your broadcast address as the target. Your broadcast address can be found in the Interfaces window.

Problems

ICMP packets cannot go backwards through a NAT (Network Address Translation) firewall or router. That means that if the address you are trying to ping has an IP starting with either "10.x.x.x" or "192.168.x.x" and you are not on the same network, the pings will always fail.
Also, some firewalls discard all ICMP packets for security. This is because more complex implementations of ICMP can be used maliciously. A common malicious use of ICMP is known as the "Ping of Death". On older computers this can crash the network interfaces and sometimes the whole operating system, which is fatal for servers. Now it is very rare to have a problem with ICMP attacks, however they do happen (to my ISP anyway).

<< Back to Index



© Charlie Boisseau 2005
52.91.221.160

Valid HTML 4.01! Valid CSS!