Ошибка ssh connection refused

Введение

У вас возникли проблемы с доступом к удаленному серверу по SSH?

Если SSH отвечает сообщением “Connection refused“, вам может потребоваться изменить запрос или проверить настройку.

В этом руководстве вы найдете наиболее распространенные причины ошибки отказа в подключении SSH.

Почему происходит отказ в подключении при SSH?

Существует множество причин, по которым вы можете получить ошибку “Connection refused” при попытке подключиться по SSH к вашему серверу. Чтобы решить эту проблему, сначала нужно определить, почему система отказала вам в подключении по SSH.

Ниже приведены некоторые из наиболее распространенных причин, которые могут вызвать отказ в подключении по SSH.

Клиент SSH не установлен

Прежде чем приступать к устранению других проблем, необходимо проверить, установлен ли у вас SSH.

На машине, с которой вы получаете доступ к серверу, должен быть установлен клиент SSH.

Без правильной установки клиента вы не сможете удаленно подключиться к серверу.

Чтобы проверить, установлен ли в вашей системе клиент SSH, введите в окне терминала следующее:

ssh

Если терминал выдает список опций команды ssh, клиент SSH установлен в системе.

Однако если он отвечает “command not found“, необходимо установить клиент OpenSSH.

Решение: Установите SSH-клиент

Чтобы установить SSH-клиент на вашу машину, откройте терминал и выполните одну из перечисленных ниже команд.

Для систем Ubuntu/Debian:

sudo apt install openssh-client

Для систем CentOS/RHEL:

sudo yum install openssh-client

ssh localhost

grep Port /etc/ssh/sshd_config

На выводе отображается номер порта, как показано на рисунке ниже.

Примечание: Вы можете подключиться к удаленной системе по SSH, используя аутентификацию с помощью пароля или открытого ключа (беспарольный вход по SSH). Если вы хотите настроить аутентификацию с открытым ключом, обратитесь к разделу  🔬 Как обменяться ключом SSH для аутентификации без пароля между серверами Linux

Служба SSH не работает

Служба SSH должна быть включена и работать в фоновом режиме.

Если служба не работает, демон SSH не сможет принимать соединения.

Чтобы проверить состояние службы, введите эту команду:

sudo service ssh status

Решение: Включите службу SSH

Если система показывает, что демон SSH не активен, вы можете запустить службу, выполнив следующие действия:

systemctl start sshd

Чтобы включить запуск службы при загрузке системы, выполните команду:

sudo systemctl enable sshd

Брандмауэр препятствует подключению SSH

SSH может отказывать в подключении из-за ограничений брандмауэра.

Брандмауэр защищает сервер от потенциально опасных соединений.

Однако если в системе настроен SSH, необходимо настроить брандмауэр так, чтобы он разрешал SSH-соединения.

Убедитесь, что брандмауэр не блокирует SSH-соединения, так как это может привести к ошибке “connection refused“.

Решение: Разрешить SSH-соединения через брандмауэр

Чтобы решить проблему, о которой мы говорили выше, вы можете использовать ufw (Uncomplicated Firewall), инструмент интерфейса командной строки для управления конфигурацией брандмауэра.

Введите следующую команду в окне терминала, чтобы разрешить SSH-соединения:

sudo ufw allow ssh

Порт SSH закрыт

Когда вы пытаетесь подключиться к удаленному серверу, SSH отправляет запрос на определенный порт.

Чтобы принять этот запрос, на сервере должен быть открыт порт SSH.

Если порт закрыт, сервер отказывает в подключении.

По умолчанию SSH использует порт 22.

Если вы не вносили никаких изменений в конфигурацию порта, вы можете проверить, прослушивает ли сервер входящие запросы.

Чтобы перечислить все прослушиваемые порты, выполните команду:

sudo lsof -i -n -P | grep LISTEN

Найдите порт 22 в выводе и проверьте, установлено ли значение STATE в LISTEN.

Также вы можете проверить, открыт ли определенный порт, в данном случае порт 22:

sudo lsof -i:22

Решение: Открыть порт SSH

Чтобы включить порт 22 для прослушивания запросов, используйте команду iptables:

sudo iptables -A INPUT -p tcp --dport 22 -m conntrack --ctstate NEW,ESTABLISHED -j ACCEPT

Вы также можете открыть порты через графический интерфейс, изменив настройки брандмауэра.

Отладка и логирование SSH

Для анализа проблем с SSH в Linux можно включить режим verbose или режим отладки.

Когда вы включаете этот режим, SSH выводит отладочные сообщения, которые помогают устранить проблемы с подключением, конфигурацией и аутентификацией.

Существует три уровня :

• уровень 1 (-v)
• уровень 2 (-vv)
• уровень 3 (-vvv)

Поэтому вместо доступа к удаленному серверу с помощью синтаксиса ssh [server_ip] добавьте опцию -v и выполните команду:

ssh -v [server_ip]

В качестве альтернативы вы можете использовать:

ssh -vv [server_ip] или

ssh -vvv [server_ip]

Заключение

В этой статье перечислены некоторые из наиболее распространенных причин ошибки SSH “Connection refused”.

Чтобы устранить проблему, просмотрите список и убедитесь, что все параметры настроены правильно.

I have an Ubuntu Server 10.10 32-bit in my home. I’m making SSH connections to it from my PC via Putty.

The problem is, sometimes I’m able to login seamlessly. However, sometimes it gives me an error like this: Network error: Connection refused.

Then, I dont’t change anything, try to login a few times more, wait a while and try again. Sometimes I can log in, sometimes I cannot. It seems pretty random to me.

What can I do to solve this?

Edit:

And Sometimes, Putty gives Network error: Software caused connection abort error after displaying login as: text.

Here is the ping -t output:

Pinging 192.168.2.254 with 32 bytes of data:
Reply from 192.168.2.254: bytes=32 time=6ms TTL=64
Reply from 192.168.2.254: bytes=32 time=65ms TTL=6
Reply from 192.168.2.254: bytes=32 time=88ms TTL=6
Reply from 192.168.2.254: bytes=32 time=1ms TTL=64
Reply from 192.168.2.254: bytes=32 time=3ms TTL=64
Reply from 192.168.2.254: bytes=32 time=1ms TTL=64
Reply from 192.168.2.254: bytes=32 time=1ms TTL=64
Reply from 192.168.2.254: bytes=32 time=1ms TTL=64
Reply from 192.168.2.254: bytes=32 time=1ms TTL=64

I turned off firewall of router, and everything seems to work now. Except for that, I still can’t enter my web server by typing external IP from my PC.

Introduction

Are you having problems accessing a remote server over SSH? If SSH responds with a «Connection refused» message, you may need to modify the request or check the setup.

In this tutorial, you will find the most common reasons for the SSH connection refused error.

Why is Connection Refused When I SSH?

There are many reasons why you might get the «Connection refused» error when trying to SSH into your server. To solve this problem, you first need to identify why the system refused your connection via SSH.

Below you will find some of the most common reasons that may cause an SSH connection denial.

SSH Client Not Installed

Before troubleshooting other issues, the first step is to check whether you have SSH properly installed. The machine you are accessing the server from should have the SSH client set up. Without the correct client set up, you cannot remote into a server.

To can check if you have the SSH client on your system, type the following in the terminal window:

ssh

If the terminal provides a list of ssh command options, the SSH client is installed on the system. However, if it responds with command not found, you need to install the OpenSSH Client.

Solution: Install SSH Client

To install the SSH Client on your machine, open the terminal, and run one of the commands listed below.

For Ubuntu/Debian systems:

sudo apt install openssh-client

For CentOS/RHEL systems:

sudo yum install openssh-client

SSH Daemon Not Installed on Server

Just like you need the client version of SSH to access a remote server, you need the server version to listen for and accept connections. Therefore, a server may refuse an incoming connection if the SSH server is missing or the setup is not valid.

To check whether SSH is available on the remote server, run the command:

ssh localhost

If the output responds with «Connection refused«, move on to installing SSH on the server.

Solution: Install SSH on Remote Server

To fix the issue of a missing SSH server, refer to how to install the OpenSSH server.

Credentials are Wrong

Typos or incorrect credentials are common reasons for a refused SSH connection. Make sure you are not mistyping the username or password.

Then, check whether you are using the correct IP address of the server.

Finally, verify you have the correct SSH port open. You can check by running:

grep Port /etc/ssh/sshd_config

The output displays the port number, as in the image below.

SSH Service is Down

The SSH service needs to be enabled and running in the background. If the service is down, the SSH daemon cannot accept connections.

To check the status of the service, enter this command:

sudo service ssh status

The output should respond that the service is active. If the terminal responds that the service is down, enable it to resolve the issue.

Solution: Enable SSH Service

If the system shows the SSH daemon isn’t active, you can start the service by running:

systemctl start sshd

To enable the service to run at boot, run the command:

sudo systemctl enable sshd

Firewall is Preventing SSH Connection

SSH can refuse a connection due to firewall restrictions. The firewall protects the server from potentially harmful connections. However, if you have SSH set up on the system, you must configure the firewall to allow SSH connections.

Ensure the firewall does not block SSH connections as this may cause the «connection refused» error.

Solution: Allow SSH Connections Through Firewall

To fix the issue we mentioned above, you can use ufw (Uncomplicated Firewall), the command-line interface tool for managing firewall configuration.

Type the following command in the terminal window to allow SSH connections:

sudo ufw allow ssh

SSH Port is Closed

When you attempt a connection to a remote server, SSH sends a request to a specific port. To accept this request, a server needs to have the SSH port open.

If the port is closed, the server refuses the connection.

By default, SSH uses port 22. If you haven’t made any configuration changes to the port, you can check if the server is listening for incoming requests.

To list all ports that are listening, run:

sudo lsof -i -n -P | grep LISTEN

Find port 22 in the output and check whether its STATE is set to LISTEN.

Alternatively, you can check whether a specific port is open, in this case, port 22:

sudo lsof -i:22

Solution: Open SSH Port

To enable port 22 to LISTEN to requests, use the iptables command:

sudo iptables -A INPUT -p tcp --dport 22 -m conntrack --ctstate NEW,ESTABLISHED -j ACCEPT

You can also open ports through the GUI by altering the firewall settings.

SSH Debugging and Logging

To analyze SSH problems in Linux, you can turn on verbose mode or debugging mode. When you enable this mode, SSH prints out debugging messages which help troubleshoot issues with connection, configuration, and authentication.

There are three levels of verbosity:

• level 1 (-v)
• level 2 (-vv)
• level 3 (-vvv)

Therefore, instead of accessing a remote server using the syntax ssh [server_ip] add the -v option and run:

ssh -v [server_ip]

Alternatively, you can use:

ssh -vv [server_ip]

or

ssh -vvv [server_ip]

Conclusion

This article listed some of the most common reasons for the SSH «Connection refused» error. To troubleshoot the issue, go through the list and make sure all the settings are configured correctly.

The other common issue that you may stumble upon is SSH Failed Permission Denied. Learn what is the cause of this error and how to fix it in our article on How To Fix SSH Failed Permission Denied (Publickey,Gssapi-Keyex,Gssapi-With-Mic).

Secure Shell (SSH) is a key WordPress development tool. It grants advanced users access to key platforms and software that make coding and other tasks easier, faster, and more organized.

So if you attempt to use SSH only to see a “Connection refused” error, you may start to feel concerned. However, this is a common issue, and it’s entirely possible to fix it on your own with just a bit of troubleshooting. You’ll be back to running commands in no time flat.

In this post, we’ll discuss what SSH is and when to use it. Then we’ll explain some common reasons your connection may be refused, including in PuTTY. Finally, we’ll provide some troubleshooting tips.

Let’s dive in!

Prefer to watch the video version?

What Is SSH and When Should I Use It?

Secure Shell (SSH), also sometimes called Secure Socket Shell, is a protocol for securely accessing your site’s server over an unsecured network. In other words, it’s a way to safely log in to your server remotely using your preferred command-line interface:

Unlike File Transfer Protocol (FTP), which only enables you to upload, delete, and edit files on your server, SSH can accomplish a wide range of tasks. For instance, if an error locks you out of your WordPress site, you can use SSH to access it remotely.

This protocol also enables you to use several key developer tools, including:

• WP-CLI. The WordPress command line. You can use it for a variety of tasks, including new installations, bulk plugin updates, and media file imports.
• Composer. A PHP package manager. It enables you to implement several frameworks for use in your site’s code by pulling the necessary libraries and dependencies.
• Git. A version control system used to track changes in code. This is especially useful for teams of developers working together on a single project.
• npm. A JavaScript package manager. It includes a command-line and JavaScript software registry. Note: Kinsta customers will need an Enterprise plan in order to access this feature.

It’s important to note that using SSH is an advanced skill. Generally speaking, lay users of WordPress should contact their developers or hosting providers for help, rather than trying to resolve issues with SSH themselves.

Why Is My SSH Connection Refused? (5 Reasons for Connectivity Errors)

Unfortunately, there are many scenarios that could occur while you’re trying to connect to your server via SSH, which might result in an error reading “Connection refused”.

Below are some of the most common issues that might be causing problems for you.

1. Your SSH Service Is Down

In order to connect to your server with SSH, it must be running an SSH daemon – a program that runs in the background to listen for and accept connections.

If this service is down, you will not be able to successfully connect to your server and may receive a Connection refused error:

Your server’s SSH daemon may be down for a wide variety of reasons, including unexpected traffic spikes, resource outages, or even a Distributed Denial of Service (DDoS) attack. In addition to the troubleshooting steps we’ll mention below, you may want to contact your hosting provider to determine the root cause of the issue.

If you suspect that your SSH service might be down, you can run this command to find out:

sudo service ssh status

If the command line returns a status of down, then you’ve likely found the reason behind your connectivity error.

2. You Have the Wrong Credentials

Although it may seem too simple to be true, it’s possible that you’re just entering the wrong credentials when trying to connect to your server. There are four pieces of information needed to run SSH:

• Host name. The IP address of the server you’re trying to connect to or your domain name.
• Username. Your (S)FTP username.
• Password. Your (S)FTP password.
• Port. The default port is 22. However, some hosting providers (including Kinsta) change their SSH port number for security reasons. If this is the case, you should be able to find it by logging in to your MyKinsta dashboard.

You can also check to see which port is being used for SSH by running this command:

grep Port /etc/ssh/sshd_config

The command line should return the correct port.

Check to make sure you’re entering the right credentials and taking into account the possibility of typos or entering the wrong IP address or port.

3. The Port You’re Trying to Use Is Closed

A “port” is simply the endpoint to which you’re directed when connecting to your server. In addition to making sure you have the correct one, you’ll also want to check to see if the port you’re trying to use is open.

Any open port is a security vulnerability, as hackers can try to exploit it and gain access to the server. For this reason, unused ports are often closed to prevent attacks.

In the event that port 22, or the custom SSH port for your server, has been closed, you will likely see a Connection refused error. You can see all the ports listening on your server by running this command:

sudo lsof -i -n -P | grep LISTEN

This command should return a list of ports with the LISTEN state. Ideally, you want to see port 22 or your server’s custom SSH port listed here. If it’s not, you’ll need to reopen the port in order to connect to your server.

4. SSH Isn’t Installed on Your Server

As we briefly mentioned earlier, servers use SSH daemons to listen for and accept connections. Therefore, if the server you’re trying to connect to doesn’t have one installed, you won’t be able to access it using SSH.

Generally speaking, almost all hosting providers will have SSH daemons installed on their servers by default. This particular issue is more common on localhost or dedicated servers.

5. Firewall Settings Are Preventing an SSH Connection

Since open ports present a security risk, firewalls installed to protect servers from hackers sometimes block connections to them. Unfortunately, this means that even harmless users who are trying to SSH into their servers may receive a Connection refused error as a result of firewall settings.

If your setup appears to be in order and you still can’t connect, take a look at your firewall’s rules. You can display them in your command-line interface with the following commands:

sudo iptables-save # display IPv4 rules

sudo ip6tables-save # display IPv6 rules

Your results will vary, but you’ll want to look for these elements to determine if your firewall is blocking SSH connections:

• dport 22: This refers to the destination port, which for SSH is usually port 22 (reminder: Kinsta doesn’t use this port number).
• REJECT: This would indicate that connections are being refused from the specified destination.
• DROP: Like REJECT, this means that connections to the relevant port are being blocked.

If you search the results of the commands above for dport 22, you should be able to determine if your firewall is preventing an SSH connection. If so, you’ll have to change the rules to accept requests.

Why Does PuTTY Say Connection Refused?

PuTTY is an SSH client. If you’re familiar with FTP, this platform is the FileZilla equivalent to SSH on Windows machines. In other words, PuTTY enables users to input their credentials and launch an SSH connection:

If you’re a PuTTY user and see the Connection refused error, the cause is likely one of those listed above.

This is an SSH connectivity error like any other, and the troubleshooting tips below should work whether you’re using PuTTY, Terminal, or any other program for connecting to your server with SSH.

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How Do I Troubleshoot SSH Connectivity Errors?

When you’re experiencing an SSH connectivity error, there are a few steps you can take to troubleshoot it depending on the cause. Here are some tips for troubleshooting the reasons for a Connection refused error that we covered above:

• If your SSH service is down. Contact your hosting provider to see why your SSH service isn’t running. For localhost or dedicated servers, you can use the command sudo service ssh restart to try to get it running again.
• If you entered the wrong credentials. Once you’ve double-checked the SSH port using the grep Port /etc/ssh/sshd_config command, try connecting again with the correct details.
• If your SSH port is closed. This is usually a side effect of one of the two reasons listed below. Either install an SSH daemon on the server you want to connect to or change your firewall rules to accept connections to your SSH port.
• If SSH isn’t installed on your server. Install an SSH tool such as OpenSSH on the server you want to connect to using the sudo apt install openssh-server command.
• If your firewall is blocking your SSH connection. Disable the firewall rules blocking your SSH connection by changing the destination port’s settings to ACCEPT.

If you’re attempting to connect to your hosting provider’s server, it may be wiser to contact support than to try troubleshooting the problem yourself. Users on localhost or dedicated servers may be able to find further support on more advanced forums if none of the above solutions works.

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Summary

Being able to connect to your server with SSH is convenient in a wide range of situations. It can enable you to access your site when you’re locked out of your WordPress dashboard, run commands via WP-CLI, track changes in your site’s code with Git, and more.

Although there are several causes that could be behind your SSH connectivity error, these are a few of the most common:

1. Your SSH service is down.
2. You have the wrong credentials.
3. The port you’re trying to use is closed.
4. SSH isn’t installed on your server.
5. Firewall settings are preventing an SSH connection.