Causes and solutions of Putty connection timeout

Today, when I was operating and maintaining a server, I used the PUTTY SSH tool. There was a timeout problem when connecting here. Here is a record of the checked scheme.

1. Check server status

We check whether the status of the server is available. If you are not sure, you can restart the server. For example, some servers cannot be connected due to downtime or failed startup.

2. Check port problems

Generally, when we use PUTTY or other SSH tools to connect to the server, the SSH ports that can be used at the beginning have been set and saved, and they are not easily replaced. However, some SSH ports are blocked. I have encountered them several times before. We check the corresponding SSH port to see if it is connected. If it is not connected, we need to replace the port.

Recommended reading How to change and modify SSH ports when SSH 22 ports of Debian system are sealed Last night, I saw a netizen mention that the website in one of his servers can be accessed normally, and the VNC login server can also see it, but I cannot log in to SSH remotely through PUTTY. The port detection tool shows that port 22 is not connected. It seems that the default port 22 is blocked, and this problem has occurred before, for example, there is a server [...] Updated: 2021/12/9 read the whole passage

3. Firewall setting problem

Some of our servers use firewall security groups. You need to add SSH port pass in the security group so that you can connect to the PUTTY software.