I just dug into a "port closed" problem for transmission-daemon on a Linux machine. The port was definitely open (according to canyouseeme.org and other testing methods), but transmission-daemon couldn't confirm it.
Here's what I learned from looking into the source code:
Transmission-daemon (and probably the other transmission-xxx programs) checks whether remote peers can talk to it at a port by sending a request to http://portcheck.transmissionbt.com/{your-port-number}. This server tries to talk to a BitTorrent client at your apparent IP address and port, and returns 1 if successful, 0 if not.
The problem I was seeing was, the machine where my transmission-daemon was running, had an auto-configured IPv6 address (as well as an IPv4 address). When transmission-daemon accessed portcheck.transmissionbt.com, it was using IPv6, and portcheck.transmissionbt.com returns a 400 Bad Request response to that. When I disabled IPv6 on the machine, everything started working right.
My upstream ISP is Comcast, and I have a static IPv4 address allocated. However, the cable modem also auto-configures IPv6, and some of my computers use IPv6 when possible/available.
I don't know whether the problem is due to weird Comcast IPv6 handling/routing, incorrect IPv6 handling at portcheck.transmissionbt.com, or some other problem. But if you're having trouble with "Port Closed," this is something to check.
Transmission Port Closed [Possible Solution SOLVED]
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Re: Transmission Port Closed [Possible Solution SOLVED]
I was wondering about that myself. Thanks. (Now, if I can figure out how to disable IPv6 ...)
Re: Transmission Port Closed [Possible Solution SOLVED]
Launched AirPort Utility.app, selected my AirPort Extreme, clicked on Edit, selected Internet tab, clicked on Internet Options..., in Configure IPv6: select Link-local only.
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Re: Transmission Port Closed [Possible Solution SOLVED]
Same problem appeared again...I found a configuration line in /etc/transmission-daemon/settings.json for "bind-address-ipv6" ... deleted this and it started working, but it also automatically re-added the line (transmission-daemon updates and rewrites the settings file on the fly). I don't know if there's a reliable, permanent solution to this.
Re: Transmission Port Closed [Possible Solution SOLVED]
Try to stop your transmission-daemon, then edit settings file and finally restart the daemon.spacewrench wrote: ↑Sat Dec 29, 2018 9:45 pm Same problem appeared again...I found a configuration line in /etc/transmission-daemon/settings.json for "bind-address-ipv6" ... deleted this and it started working, but it also automatically re-added the line (transmission-daemon updates and rewrites the settings file on the fly). I don't know if there's a reliable, permanent solution to this.
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Re: Transmission Port Closed [Possible Solution SOLVED]
OMG! I've been searching weeks to solve this on my iMac.
Thank you for the solution.
System Settings>Network>Service>Details>TCP/IP>Configure IPv6>Link-Local Only
Brilliant.
Thank you for the solution.
System Settings>Network>Service>Details>TCP/IP>Configure IPv6>Link-Local Only
Brilliant.
Re: Transmission Port Closed [Possible Solution SOLVED]
Same here! It was doing my head in until I found this ..thanks too!
As the port is open but just not showing as open, just wonder is it ok to leave things as they as is?
What would i notice apart from the port open warning to tell me that others can connect to me at that port?
As the port is open but just not showing as open, just wonder is it ok to leave things as they as is?
What would i notice apart from the port open warning to tell me that others can connect to me at that port?