bash: iptables: command not found

Ok, first things first, I must tell you that, if you are on a school, university, work, company, or other network outside your control, it is unlikely that this page will help you. Being on a network where you have no access whatsoever to the firewall or router settings of the network, and no knowlege of the actual upstream/downstream capacity of the internet connection, means that you will not be able to access the settings of that network. This means you will not be able to open access through the settings made by the organisation which owns the network you use. Having said that, give it a go anyway, you might have a slim chance of being lucky. 🙂

You may be thinking, „But I did all this already! It was all working beautifully before, and now that I installed a new version of Azureus I’m back to the yellow smilies and NAT error!” Well, if this is indeed the case, try going to: Plugins->UPnP UPnP is short for Universal Plug and Play, it is a feature that works with some compatible routers to open the required ports automatically. However, some routers, even if they are compatible with UPnP, have problems with this. So untick the box that says Enable UPnP and click Save at the bottom left of the Azureus window. Then you may wait awhile and see if there is any improvement.

If you are in a rush, you can stop all your torrents, go to Tools>Configuration Wizard and test your TCP listen port there. If you are still getting NAT error, then please continue down the rest of this page. If you get ….OK! then there is nothing more you need do with ports for now. 🙂
Yellow Smilies: The smiley faces are indicators for what is going on with your torrents. The yellow smiley is an indicator that, although your system is able to initiate connections with other peers (known as local connections, or L), you are not able to receive connections initiated from other peers (known as remote connections, or R). When you are not able to receive remote connections, this is nearly always to do with incorrectly forwarded ports, from your router or firewall. You can see the L’s and R’s in the Details view of your individual torrent tabs. If you only see L connections, chances are you have a Port Forwarding problem. Green smileys mean that you have both L and R connections to peers, and that you are connected to the tracker. For more information on what all the smileys mean, ctrl-click (Mac) or right-click (win) in the „Health” column in the My Torrents view, and select Health Column>About Health. Yellow smilies are not in themselves a bad sign. If you can get even one green smiley, or have had one in the past, then your issues are probably not to do with port forwarding. It is only when you only ever get the yellow smiles, and never get the green ones that port forwarding is an issue. So remember, yellow smilies are ok if you have also got even one green one, ok? 🙂
Ports: When you are connected to the internet, there are many different, um, sort of channels that information travels back and forth in. Mostly you will have no reason to notice these, because information automatically travels in and out of the port that it, um, kind of, belongs to. Ports are identified by numbers. Like, for example, MSN protocol usually uses ports 6891-6900.

Please see PortIsBlacklisted now for important information on which ports to use. You can go to this site: http://ports.tantalo.net/ and this site: http://en.wikipedia.org/wiki/List_of_well-known_ports_%28computing%29 to find out more about which ports belong to which protocols. 🙂

Azureus only uses ONE listen port. (plus one for the embedded tracker) Both TCP and UDP are used,but on the same port. So you will ONLY need to forward one listening port for Azureus, and you will need to tick both the TCP box and the UDP box.

Anyway, the only time you will notice the ports is when they are closed, and won’t allow any information to travel. This is the situation when you get those error messages like „NAT Error”, or similar. Ports are mostly closed by firewalls, and routers.

NAT: is short for Network Address Translation. This means that the Network, (which consists of any and all hardware you have connected up together, such as your router and your computer) needs to Translate the IP address of your router (which has it’s own IP address) to and from the IP address of your computer (which also has it’s own, different IP address). In simpler terms, it’s sort of like mail forwarding. The router is there to help protect you from what it thinks is unwanted traffic, it is sort of like the Post Office. Inside the router, the port forwarding instructions are like telling the postman to redirect your mail to a different address. So the original address from the outside world (WAN, or Wider Area Network) is the IP address of your router, that’s what the postman sees on the labels of parcels and letters. Then the postman redirects your mail according to the instructions you gave, to your ACTUAL address, which is the real local IP address of your computer, in the LAN (Local Area Network). See below for how to find out what the actual IP of your computer is on Mac OS X.

So when you get the error message „NAT Error”, this means that your router is NOT translating the IP address from your computer to and from the outside world IP address of your router. And this is why no information or downloads can occur until this is sorted out, because information can not pass between your computer and the router, and thus cannot pass to and from the outside world of the internet.

Sorry if this is confusing! I’m doing the best I can, it’s a tricky subject. Hopefully the diagram below will demonstrate why port forwarding is needed and how it works.. 🙂 WhatIsNat might help too.

Port Forwarding: Port Forwarding is when your firewall or router accepts incoming or routes outgoing information through the ports, and forwards this information to and from your computer. So it is very important when using the internet to forward the ports you will be using, so that you may send and receive the information you want. And if you have both a firewall AND a router, it is necessary to forward the ports in BOTH.