I still seem to be facing connection issues. Why is that?
nc -vvv feed.community.greenbone.net 873 gives connection refused too.
nc -vvv feed.community.greenbone.net 873 gives connection refused too.
io timeout is a failure on your side, and your TCP connection is not correctly terminated.
Advice remove NAT device, connect your system direct to the internet.
just confused⌠sometimes nc -vvv feed.community.greenbone.net 873 worksâŚ
And I confirmed there is no NAT device and firewall doesnât have natting nor is it blocking anything.
Can I do anything about the TCP connection that didnât terminate properly?
Do you run on a native server or any hypervisor ? Be sure you have a briged connection.
Its a running on hypervisor. Not sure about the bridged connection. But it was working a week ago so I think this should not be the problem?
There could be your NAT gateway 
From my hetzner server I get 0 connections to the feeds unfortunatly.
from my office I do get a feed connection, but as I want to install 3 sensor systems in our 3 offices, I thought to offload the community feed by mirroring it to our central server, unfortunatly⌠that one does not sync 
Iâm having severe problems since the changes done lately as well, while the nightly cronjob worked well and without any issues in the past, now it doesnât and I have to manually try multiple times to eventually get a successfull sync done for every single feed which is a huge annoyance. We donât have any occurances in our firewall logs and like stated it worked just fine in the past, no changes done on our side.
host ~ # su -c greenbone-nvt-sync -s /bin/bash gvm
rsync: [Receiver] failed to connect to feed.community.greenbone.net (45.135.106.142): Connection timed out (110)
rsync: [Receiver] failed to connect to feed.community.greenbone.net (2a0e:6b40:20:106:20c:29ff:fe67:cbb5): Network is unreachable (101)
rsync error: error in socket IO (code 10) at clientserver.c(137) [Receiver=3.2.3]
host ~ # su -c greenbone-nvt-sync -s /bin/bash gvm
rsync: [Receiver] failed to connect to feed.community.greenbone.net (45.135.106.142): Connection timed out (110)
rsync: [Receiver] failed to connect to feed.community.greenbone.net (2a0e:6b40:20:106:20c:29ff:fe67:cbb5): Network is unreachable (101)
rsync error: error in socket IO (code 10) at clientserver.c(137) [Receiver=3.2.3]
host ~ # time su -c greenbone-nvt-sync -s /bin/bash gvm
rsync: [Receiver] failed to connect to feed.community.greenbone.net (45.135.106.142): Connection timed out (110)
rsync: [Receiver] failed to connect to feed.community.greenbone.net (2a0e:6b40:20:106:20c:29ff:fe67:cbb5): Network is unreachable (101)
rsync error: error in socket IO (code 10) at clientserver.c(137) [Receiver=3.2.3]
real 2m17,192s
user 0m0,032s
sys 0m0,029s
host ~ # time su -c greenbone-nvt-sync -s /bin/bash gvm
rsync: [Receiver] failed to connect to feed.community.greenbone.net (45.135.106.142): Connection timed out (110)
rsync: [Receiver] failed to connect to feed.community.greenbone.net (2a0e:6b40:20:106:20c:29ff:fe67:cbb5): Network is unreachable (101)
rsync error: error in socket IO (code 10) at clientserver.c(137) [Receiver=3.2.3]
real 2m14,817s
user 0m0,032s
sys 0m0,028s
host ~ # time su -c greenbone-nvt-sync -s /bin/bash gvm
rsync: [Receiver] failed to connect to feed.community.greenbone.net (45.135.106.142): Connection timed out (110)
rsync: [Receiver] failed to connect to feed.community.greenbone.net (2a0e:6b40:20:106:20c:29ff:fe67:cbb5): Network is unreachable (101)
rsync error: error in socket IO (code 10) at clientserver.c(137) [Receiver=3.2.3]
real 2m14,870s
user 0m0,037s
sys 0m0,023s
host ~ # time su -c greenbone-nvt-sync -s /bin/bash gvm
rsync: [Receiver] failed to connect to feed.community.greenbone.net (45.135.106.142): Connection timed out (110)
rsync: [Receiver] failed to connect to feed.community.greenbone.net (2a0e:6b40:20:106:20c:29ff:fe67:cbb5): Network is unreachable (101)
rsync error: error in socket IO (code 10) at clientserver.c(137) [Receiver=3.2.3]
real 2m14,215s
user 0m0,039s
sys 0m0,020s
host ~ # time su -c greenbone-nvt-sync -s /bin/bash gvm
rsync: [Receiver] failed to connect to feed.community.greenbone.net (45.135.106.142): Connection timed out (110)
rsync: [Receiver] failed to connect to feed.community.greenbone.net (2a0e:6b40:20:106:20c:29ff:fe67:cbb5): Network is unreachable (101)
rsync error: error in socket IO (code 10) at clientserver.c(137) [Receiver=3.2.3]
real 2m15,974s
user 0m0,037s
sys 0m0,022s
That issue should be solved here, please read the important new rules !
If you try to brute force the synchronization, you will never be able to sync again.
The following IPs tried to sync more then 10.000 Times in the last 20h. Please keep in mind, >10 TCP SYN to any port within one minute and your source IP will be blocked for 24h automatically.
11343 194.33.xx.xx
11629 216.56.xx.xx
12109 103.231.xx.xx
13380 96.67.xx.xx
14733 212.34.xx.xx
16457 183.239.xx.xx
17674 85.199.xx.xx
19633 74.206.xx.xx
20279 24.119.xx.xx
20702 62.76.xx.xx
27654 69.63.xx.xx