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What Aspect Of Emule Requires Port Forwarding?

#1 User is offline   silver123 

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Posted 28 May 2023 - 04:25 AM

Hi, I understand that port forwarding allows internet devices access to local LAN resources. But why does emule require it when qbittorrent doesn't when searching/downloading/uploading files. What aspect of emule in specific requires port forwarding enabled? As an extension to this question, when would qbittorrent require port forwarding, as it does have that option in its settings?

Thanks for any help.
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#2 User is offline   DJKuhpisse 

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Posted 28 May 2023 - 09:09 AM

eMule only supports IPv4, an old protocol from the 80s that is still in use today, but very nasty. Torrent also supports IPv6, which does not have the problems of IPv4.

Because IPv4 has 32 bit addresses, there are not enough for every computer. Your router has a public one that is unique in the internet, your PC doesn't. The router translates them when outgoing traffic (like sending an email) is happening. Now someone wants to connect to your emule to doenload, the router needs to know which internal machine should receive the traffic. This is a static NAT rule and called port forwarding.

If there are 2 users that have a low ID (no port forwarding in the router configured or wrong), they can't connect to each other.
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#3 User is offline   megaT 

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Posted 28 May 2023 - 09:55 AM

Though to elaborate a bit more on that,
you still have to actually allow that port access in your router/gateway/switch despite IPv4 or IPv6.

A lot of people mistakenly perceive IPv6 as being more insecure than IPv4, but that's not the case - IPv6 was designed without NAT
because we've more than enough address space with it.
However, also due to a number of other reasons later on NATv6 was invented - so providers and other facilities still have an option on NAT in IPv6 if they want.

IPv6 itself is not a security problem, whether you have a global address on your local machine or not, will not undo the requirement that you actually have to allow a port in your firewall/router.
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#4 User is offline   silver123 

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Posted 28 May 2023 - 11:49 AM

Thanks for that. So just to rephrase my understanding:
  • With emule, since it only uses IPv4, I need to set up port forwarding so internet devices can initiate communication with my emule client. i.e. they need to know which internal IP to route traffic on that port.
  • With qbittorrent, if I choose to only allow it to use IPv4, I need to set up port forwarding. However if I allow it to use IPv6, I don't need port forwarding as my PC's IPv6 address will be publicly visible within the torrent network, and internet devices can initiate communications with my qbittorrent client.


Thanks.
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#5 User is offline   megaT 

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Posted 28 May 2023 - 12:14 PM

It's not exactly like this, sadly most SOHO devices keep using port forwarding / forwarding and related terms as comparable.
This is due to reasons that inexperienced people require to find these options, after all these devices are about to be used by non-IT people maybe.

Most likely you'll always need to setup correct port forwarding, irrelevant if you are a IPv4 or a IPv6 user.
First of all we live in a dual-stack world, so if you use IPv6... most likely you use IPv4 too. The user isn't really conscious about what he/she is using or not is using.
Second regardless if you have a global routable address available, you still need to make the port accessible (eg. the router/gateway shall not block this).

Technically NAT and port forwarding are two separate things - but often used interchangeably which is wrong.
Your router will most likely do the right thing and also do NAT if required, but NAT doesn't render forwarding obsolete - in fact also IPv6 requires to be forwarded thru a gateway (the router).
Routing and port forwarding are two separate aspects, your IPv6 address may be global routable but you still need to forward (allow) the packets through your router.
(Otherwise this would be a big security risk the user wouldn't know and normally those typical devices will block everything at default)
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#6 User is offline   DJKuhpisse 

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Posted 28 May 2023 - 01:15 PM

If you don't use NAT for IPv6 (NAT with IPv6 is uncommon), you don't need a static NAT rule (port forwading). If your router acts as an SPI firewall (most routers have it), you need a firewall exception. This is different from a port forwarding.
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