Local Port Scanner Local Port Scanner v1.2.2 Copyright © 1997-2001 JPSoft DK
This software is freeware and used at your own risk
 


What's new:
The following new features were added to v1.2.2:

1) Fixed some small bugs. One was LPS only scanning well known TCP Ports up to 1024
when Full TCP Scan was selected.
2) Added Trace Route functionality (some of the ICMP protocol's functions).

So, what is Trace Route?
Trace Route can used in order to test your network connectivity.
Traceroute sends a packet of data to the host you specify in the traceroute
query and tracks progress along the way.
Traceroute tells you the hostnames of the routers which connect our network to the
destination host.
Traceroute reports the time a packet takes to get through each router
along the path.


ICMP Protocol Overview
Internet Control Message Protocol (ICMP), documented in RFC 792, is a required protocol tightly integrated with IP. ICMP messages, delivered in IP packets, are used for out-of-band messages related to network operation or mis-operation. Of course, since ICMP uses IP, ICMP packet delivery is unreliable, so hosts can't count on receiving ICMP packets for any network problem. Some of ICMP's functions are to:

  • Announce network errors, such as a host or entire portion of the network being unreachable, due to some type of failure. A TCP or UDP packet directed at a port number with no receiver attached is also reported via ICMP.
  • Announce network congestion. When a router begins buffering too many packets, due to an inability to transmit them as fast as they are being received, it will generate ICMP Source Quench messages. Directed at the sender, these messages should cause the rate of packet transmission to be slowed. Of course, generating too many Source Quench messages would cause even more network congestion, so they are used sparingly.
  • Assist Troubleshooting. ICMP supports an Echo function, which just sends a packet on a round--trip between two hosts. Ping, a common network management tool, is based on this feature. Ping will transmit a series of packets, measuring average round--trip times and computing loss percentages.
  • Announce Timeouts. If an IP packet's TTL field drops to zero, the router discarding the packet will often generate an ICMP packet announcing this fact. TraceRoute is a tool which maps network routes by sending packets with small TTL values and watching the ICMP timeout announcements.

Bold items are implemented by the Trace Route function.

More information on ICMP can be found at http://www.freesoft.org/CIE/Topics/81.htm.