# Solution for SSH Proxy Connection Error: Connection Closed by Foreign Host


## 1. Background

The first time I used a foreign VPS, I wondered how I could speed up the connection to it. I noticed there was a proxy option in SSH software - for example, Xshell has a proxy option in its session properties. After setting up and adding a proxy server, double-clicking the session to SSH connect to the foreign VPS didn't succeed. Instead, I got the error message shown below.

![Xshell initial proxy connection to Bandwagon VPS unsuccessful](https://vip2.loli.net/2022/10/06/5AjmBMCSaDZpJGf.png)

I looked at many solutions online, and one method worked: using a domestic cloud service provider like Alibaba Cloud to connect to the foreign VPS - the speed was much faster than directly using an SSH tool locally (without a proxy).

I tried it myself and set up an intermediate forwarding server through Alibaba Cloud in Termius SSH software. Connecting to the foreign VPS again was very fast.

Out of curiosity, I started researching SSH proxy connections to foreign VPS and even asked people in Telegram groups. I found that my SSH software settings were correct, and others could successfully connect to foreign VPS through SSH proxy with the same settings, but mine didn't work.

However, when I switched to my self-hosted proxy node, I successfully connected to the foreign VPS. Using commercial proxy service nodes still resulted in the error shown above.

## 2. Solution

First, make sure the proxy is properly configured in your SSH software.

Change the default SSH port `22` on the foreign VPS to something like `23456`.

```shell
# Process to change SSH port on Ubuntu
# Open the SSH configuration file with vim editor
vi /etc/ssh/sshd_config

# In command mode, press G (uppercase) to jump to the last line of the file
# Change the default SSH port 22 to 23456
PasswordAuthentication yes
PermitRootLogin yes
+ Port 23456

# Restart the SSH service
/etc/init.d/ssh restart
```

Then try using the commercial proxy service node again, and you should be able to successfully connect to the foreign VPS.

## 3. Root Cause

Most commercial proxy services have auditing in place, which may block the SSH protocol. This prevents you from using the proxy to connect to port `22` on foreign VPS.

> Why do most commercial proxy services block the SSH protocol?

![Reason 1 why proxy services block SSH protocol](https://vip2.loli.net/2022/10/06/QHnjU9pqyEfXko7.png)

![Reason 2 why proxy services block SSH protocol](https://vip2.loli.net/2022/10/06/gySPfXzAYVFdn9u.png)

Simply put, this port could be abused, and abuse causes trouble for the provider. For example, most cloud service providers block SMTP port `25` to prevent people from sending spam emails.

> Why is connecting to a foreign VPS through domestic cloud service providers like Alibaba Cloud faster than using SSH software directly (without a proxy)?

![Reason why connecting through domestic VPS to foreign VPS is faster than direct connection](https://vip2.loli.net/2022/10/06/DScJHjIoWXhZ5Mq.png)

Alibaba Cloud's routing to your foreign VPS is better optimized than your direct connection to the foreign VPS.