使用Ngrok建立Google Colab SSH隧道时遭遇ConnectionRefusedError

问题概述 #

尝试使用Ngrok为Google Colab实例建立SSH隧道时，出现ConnectionRefusedError，提示无法建立连接，可能原因包括Ngrok配置错误、防火墙限制、端口转发不正确、Colab实例问题或Ngrok免费版限制等。

报错详情 #

ConnectionRefusedError                    Traceback (most recent call last)
/usr/local/lib/python3.10/dist-packages/urllib3/connection.py in _new_conn(self)
    202         try:
--> 203             sock = connection.create_connection(
    204                 (self._dns_host, self.port),

18 frames
ConnectionRefusedError: [Errno 111] Connection refused

The above exception was the direct cause of the following exception:

NewConnectionError                        Traceback (most recent call last)
NewConnectionError: <urllib3.connection.HTTPConnection object at 0x7cda712b1f90>: Failed to establish a new connection: [Errno 111] Connection refused

The above exception was the direct cause of the following exception:

MaxRetryError                             Traceback (most recent call last)
MaxRetryError: HTTPConnectionPool(host='localhost', port=4040): Max retries exceeded with url: /api/tunnels (Caused by NewConnectionError('<urllib3.connection.HTTPConnection object at 0x7cda712b1f90>: Failed to establish a new connection: [Errno 111] Connection refused'))

During handling of the above exception, another exception occurred:

ConnectionError                           Traceback (most recent call last)
/usr/local/lib/python3.10/dist-packages/requests/adapters.py in send(self, request, stream, timeout, verify, cert, proxies)
    517                 raise SSLError(e, request=request)
    518 
--> 519             raise ConnectionError(e, request=request)
    520 
    521         except ClosedPoolError as e:

ConnectionError: HTTPConnectionPool(host='localhost', port=4040): Max retries exceeded with url: /api/tunnels (Caused by NewConnectionError('<urllib3.connection.HTTPConnection object at 0x7cda712b1f90>: Failed to establish a new connection: [Errno 111] Connection refused'))

执行的操作步骤 #

# Install useful stuff
!apt-get update > /dev/null
!apt-get install --yes ssh screen nano htop ranger git > /dev/null

# SSH setting
!echo "root:hello" | chpasswd
!echo "PasswordAuthentication yes" > /etc/ssh/sshd_config
!echo "PermitUserEnvironment yes" >> /etc/ssh/sshd_config
!echo "PermitRootLogin yes" >> /etc/ssh/sshd_config
!service ssh restart > /dev/null

# Download ngrok
!wget -q -c -nc https://bin.equinox.io/c/4VmDzA7iaHb/ngrok-stable-linux-amd64.zip
!unzip -qq -n ngrok-stable-linux-amd64.zip

# Run ngrok
authtoken = "2LSXUPuvhq7GioEKGLXOsTX4tUT_RX5wTzEfvKUTwZAkHfyo"
get_ipython().system_raw('./ngrok authtoken $authtoken -region ap && ./ngrok tcp 22 &')
!sleep 3

# Get the address for SSH
import requests
from re import sub
r = requests.get('http://localhost:4040/api/tunnels')
str_ssh = r.json()['tunnels'][0]['public_url']
str_ssh = sub("tcp://", "", str_ssh)
str_ssh = sub(":", " -p ", str_ssh)
str_ssh = "ssh root@" + str_ssh
print(str_ssh)

排查与解决方法 #

• 验证Ngrok认证令牌：确认authtoken正确，无过期或输入错误，替换为从Ngrok控制台获取的有效令牌后重新运行脚本。
• 确认Ngrok进程状态：运行!ps aux | grep ngrok检查Ngrok是否启动。若未启动，拆分Ngrok命令分步执行，避免前序命令失败导致后续不执行：

  !./ngrok authtoken $authtoken -region ap
  !./ngrok tcp 22 &
  

• 延长启动等待时间：将!sleep 3改为!sleep 5或!sleep 10，确保Ngrok的API服务（4040端口）完全启动后再请求隧道信息。
• 检查SSH服务状态：执行!service ssh status确认SSH服务正常运行，若未启动重新执行!service ssh restart，同时检查sshd_config配置项是否生效。
• 确保Colab实例活跃：Colab免费实例可能因闲置被回收，重启Colab运行时后重新执行脚本，确保实例处于活跃状态。
• 检查端口占用：执行!lsof -i :4040查看4040端口是否被占用，若有占用可杀掉对应进程，或通过--api-port指定其他端口：

  !./ngrok tcp 22 --api-port 4041 &
  

  同时将请求URL改为http://localhost:4041/api/tunnels。
• 检查Ngrok免费版限制：免费版Ngrok有并发连接和隧道数量限制，若超出限制等待一段时间后重试，或考虑升级付费版。

内容的提问来源于stack exchange，提问作者Jhngir Khn