troubleshooting Question

Odd ftp / ssh connection problem - diagnosis required please

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xoundboy asked on
SSH / Telnet SoftwareServer SoftwareLinux Distributions
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Although my production VPS (Centos 5 with LXadmin hosting control panel) is happily serving my websites I can't connect to it through SSH or FTP. I get an error - "Server unexpectedly closed connection" from WinSCP and similar errors from other FTP / SSH clients.

It's a problem that has just started occuring within the past 24 hours and appears to possibly be related to my IP address. Here are the steps I have taken so far to try to diagnose the problem:

1. At first  I thought my server OS must be corrupt so I restored the system template from the hosting hypervisor panel. This made no difference.

2. Then I contacted the VPS host company to check whether there was a problem there but they said they had no problem connecting to my VPS through either protocol.

3. I then got a friend to test it from the other side of town and he can connect too without a problem.

4. I then logged into another friend's VPN, based in a different country, and through that could connect successfully to my VPS from my home laptop no problem.

5. I then logged into my next door neighbour's wifi network and tried to log in - but couldn't.

This made me think that my internet connection provider might have begun blocking traffic on ports 21 and 22 so....

6. I checked my computer's  and router's firewalls. Both allow ports 21 and 22 to pass through

7. I checked to see if I could log into other servers that I run through SSH/ FTP - this I can do no problem.

 Basically it would appear that my VPS is  accepting connections from pretty much everywhere except me and my next door neighbour. I thought I might ring my home connection provider and tell them that I can connect to one server but not another through ssh/ftp but I know they would just tell me that it's a problem with my server. Now I've run out of ideas for how to diagnose the problem. Please can someone help me. I can't carry on using the VPN connnection for working on the VPS - it's really slow.

Thanks in advance.

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