Here is the situation:
We have couple of computers in office but only two of them have issues connecting to our company website. Both runs ubuntu.
It's always like this: I can connect to website 3-4 times fine then all TCP packet are retransmitted without success (see screenshot). And for couple of minutes I can't connect to anything TCP-related. Then I can connect. Then again error, loop.
Same error happen with FTP - I can connect to FTP, it works fine for first few commands then it's dead for couple of minutes.
I can ping server constantly with zero issues, we changed router, called ISP, everything is fine.
Issue is strange because of symptoms:
- issue appears with only that website everything on internet used to works fine for years but on another hand that website works just everywhere even on same computers with windows
- when I connect to SSH I can stay connected forever. even if I get retransmission errors later on..
- but if I got retransmission errors before I connecto to SSH I can't connect to SSH anymore!
- Ping is always fine, so traceroute/mtr
- Works fine on CentOS server and Windows computers in office
- Works fine on same ubuntu machines when booted into Windows
- I disconnected all devices except my work ubuntu laptop, tried, still same issue
This is script I wrote to check does issue exists:
#!/bin/bash while : do if ! [ $(curl --silent --connect-timeout 1 "our-website.com" | wc -l) -eq 12 ]; then echo "ERR" else echo "OK" fi; sleep 1 done
Last test with brand new router gave me 648 x OK, 562 x ERR
Our CentOS server gives me 100% x OK
This was tested on (Ubuntu 14.04.2 LTS):
Linux 3.13.0-55-generic #94-Ubuntu SMP Thu Jun 18 00:27:10 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux
Linux 3.16.0-41-generic #57~14.04.1-Ubuntu SMP Thu Jun 18 18:01:13 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux
One computer uses default network manager, another one wicd network manager.
I tried other kernels no success.
I also tried to change
sysctl net.ipv4.tcp_sack sysctl net.ipv4.tcp_syn_retries /proc/sys/net/ipv4/tcp_retries1
And no success. It might sound like question for server fault but error happens only on Ubuntu so that's why I ask my question here.
You could say this is hosting problem, but no, I talked to hosting a lot, no help. We use shared hosting and none of their customers had similar issue, also I can confirm it works everywhere else.
I blurred server's IP address but I decided to publish IP of server/url, here it is: http://126.96.36.199:2222 - after few browser refreshes it stops working, every time