February 2000
Intermediate to advanced
464 pages
15h 57m
English
Content preview from Internet Core Protocols: The Definitive Guide
Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.
ICMP Destination Unreachable: PortUnreachable Error Messages
In order to effectively debug problems with UDP delivery, you should rely on the ICMP protocol. It is the function of ICMP to report on problems that will keep IP datagrams (or UDP messages) from getting delivered to their destination effectively. For more information on ICMP, refer to Chapter 5.
Figure 6.8 shows a problem with a TFTP client being unable to send data to a TFTP server. In this example, Greywolf has attempted to send data to Arachnid using TFTP. However, Arachnid is not running a TFTP server at this moment, so it returns an ICMP Destination Unreachable: Port Unreachable Error Message back to Greywolf.
Figure 6.8. An ICMP Destination Unreachable: Port Unreachable Error
Message
If an application receives an ICMP error in response to an action, either it may try to send the data again or it may give up on the operation. Either way, any error-correction services must be implemented by the application, and not by UDP.
Another important point to make here is that many applications will not intercept or display ICMP Error Messages to the users of the application. Therefore, in order to diagnose problems such as this, it may be necessary to capture and decode the traffic on your network, using a tool such as Shomiti’s Surveyor Lite.
Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
and much more.
Read now
Unlock full access
More than 5,000 organizations count on O’Reilly
O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.