This topic provides answers to frequently asked questions about how to connect to a simple application server.

Troubleshooting procedure

If you cannot connect to a simple application server, we recommend that you troubleshoot the problem based on the following procedure. The troubleshooting procedure is sorted by the probability of the causes. We recommend that you troubleshoot the problem in order. This helps you quickly identify the cause of the problem. If the problem persists after you try a possible solution, proceed to the next one until the problem is solved.
Procedure Operation
Check whether the server status is abnormal. Only simple application servers that are in the Running state allow users to log on.
  • If the status of the server is Stopped, restart the server.
  • If the status of the server is Disabled, perform the following operations:
    • Check whether the server is expired. If the server is expired, renew the server. For more information, see Upgrade and renew a simple application server.
    • Check whether you have an overdue payment for the server. If you have an overdue payment for the server, add funds to the account.
For information about how to view the status of a server, see View server information.
Check whether the logon credential is invalid. Make sure that you use a valid username and password or key pair to log on to the server.
  • If you forget the password, you can reset the logon password by using the password resetting feature. After you reset the password, restart the simple application server to allow the new password to take effect. For more information, see Manage the password of a server.
  • If the key pair is invalid, change the key pair. For more information, see Change a key pair.
  • If you use the Simple Application Server console to log on to the server but fail, submit a ticket to allow Alibaba Cloud to check whether the key file was deleted by mistake.
Check whether the port configurations are correct. Check whether the logon port is enabled on the firewall. The default logon port is port 22 for Linux servers and port 3389 for Windows servers. If the corresponding port is not enabled, enable it. For more information, see Manage the firewall of a server.
Check whether the firewall is enabled. If the server runs a Windows OS, disable the firewall.
Check whether the server is deployed outside the Chinese mainland. If you are in the Chinese mainland and attempt to connect to a simple application server in a region outside the Chinese mainland, latency and packet loss may occur, which causes the server to be inaccessible. This is a problem with the Internet service providers and cannot be solved on the server. For more information, see What do I do if I am prompted that the connection has timed out when I connect to a simple application server outside the Chinese mainland?
Check whether the network is stable Use an on-premises host in another network environment to connect to the simple application server, or use another wireless network such as a mobile phone hotspot to test the access. This measure can help you find out whether the connection fails due to a local network problem. If a local network problem causes the connection failure, we recommend that you contact the local network provider to solve the problem.
Check whether the server is overloaded. If the utilization of the bandwidth or vCPUs of the simple application server is excessive, you may fail to log on to the server.
To solve the problem, perform the following operations:
Check whether an antivirus software blocks the connection. Third-party antivirus software may cause the failure of connection to the simple application server.
  • If a third-party antivirus software is running, check whether the antivirus software blocks the connection to the simple application server. If the antivirus software blocks the connection, add the public IP address of the simple application server to the whitelist, and then retry the connection.
  • You can also disable or uninstall the third-party antivirus software and try again.
Check whether the server is infected by viruses such as mining viruses. If blackhole filtering is triggered for the public IP address of the simple application server due to attacks, you can manually deactivate blackhole filtering and try the connection again. For more information, see Blackhole filtering policy of Alibaba Cloud.
Check whether the Remote Desktop Protocol (RDP) of the server is enabled. If the simple application server runs a Windows OS, check whether the RDP is enabled. If the RDP is disabled, enable it. For more information, see How do I troubleshoot the failure to connect to a Windows server while no error message appears?.
Check the specific error message of the connection Troubleshoot the problem based on the specific error message. For more information, see FAQ navigation.

If the problem persists after you take the preceding measures, submit a ticket to contact technical support.

FAQ navigation

What do I do if I am prompted that the connection has timed out when I connect to a simple application server outside the Chinese mainland?

If you are in the Chinese mainland and attempt to connect to a server in a region outside the Chinese mainland, latency and packet loss may occur, which causes the server to be inaccessible. This is a problem with the Internet service providers and cannot be solved on the server. For information about the regions where Simple Application Server is supported, see Regions and network connectivity. You can use one of the following methods to solve this problem:
  • If the network inaccessibility problem is not a consistent problem, you can change the local network environment or try to connect to the server later.
  • If your server is not required to be deployed in a region outside the Chinese mainland, we recommend that you request a refund for your server and purchase a server deployed in the Chinese mainland.
    Note If you cannot request refunds for servers,submit a ticket.

How do I apply for unlocking the public IP address of the server?

If a server is locked because it is infected by mining viruses or attacked, you can apply for unlocking the server. To apply for unlocking servers, go to the Penalties page in the Security Center.
Note
  • You can apply for unlocking servers in your account only once.
  • A server that has been unlocked is automatically checked after 3 days. If a mining program is detected on the server again, the server is locked and cannot be unlocked.
  • After the server is unlocked, back up the data on the server at your earliest opportunity.

Why am I prompted that the connection is rejected when I fail to connect to my server?

This may be caused by one of the following issues. Troubleshoot these issues:
  • The remote service that corresponds to SSH or RDP is not enabled on the server.
  • Ports used for remote connections, such as SSH port 22 and RDP port 3389, are not enabled on the server.

Why am I prompted that the username or password is incorrect when I fail to connect to the server?

The username or password that you entered is incorrect. Perform the following operations:
  • Enter the correct username. The username is root for Linux servers and administrator for Windows servers.
  • Enter the correct password. If you forget your password, you can reset it. For more information, see Manage the password of a server.
  • If you log on to the Windows server as a non-administrator user, the user must belong to the Remote Desktop Users group.

What do I do if the connection to a Linux server fails when SELinux is enabled on the Linux server?

For information about how to solve this problem, see What do I do if an SSH remote connection exception due to SELinux being enabled occurs on a Linux instance?

If Security-Enhanced Linux (SELinux) is enabled, system security can be enhanced. However, after SELinux is enabled, the files of the operating system are damaged, and failures occur on system startup. We recommend that you enable or disable SELinux in an appropriate manner to prevent the system from failing to start up. For more information, see Enable or disable SELinux.

What do I do if an authentication problem occurs when I connect to a Windows server?

This problem may be caused by upgrade patches released by Windows. For information about how to solve this problem, see the following topics:

What do I do if I cannot connect to a Windows server by using the administrator account?

If you configure security policies on your Windows computer to deny logons from terminal services, you cannot use Remote Desktop Connection (RDC) on your Windows computer to connect to a Windows server by using the administrator account. For information about how to solve this problem, see What do I do if I cannot connect to a Windows instance by using the administrator account?

How do I troubleshoot the failure to connect to a Windows server while no error message appears?

This problem occurs when you use the RDC tool on your Windows computer to connect to a Windows server. This may be because remote connection permissions are not enabled on the Windows server. In this example, Windows Server 2012 R2 64-bit is used to describe how to solve this problem.
  1. Use the Simple Application Server console to connect to the Windows server.

    For more information, see Use the Simple Application Server console to connect to a Windows server.

  2. Open This PC. In the left-side navigation pane, right-click This PC and select Properties.
  3. In the left-side navigation pane of the System page, click Remote settings.
  4. In the Remote Desktop section of the System Properties dialog box, select Allow remote connection to this computer.
  5. Click Apply and then click OK.

    After the configurations are complete, you can try to connect to the server again.

What do I do if the "The remote computer that you are trying to connect to requires Network Level Authentication (NLA)" message is prompted when I connect to a Windows server?

When you use the RDC tool on your Windows computer to connect to a Windows server, the message may be prompted. This may be because the RDC tool on your computer is of an earlier version. In this example, Windows Server 2012 R2 64-bit is used to describe how to solve this problem.
  1. Use the Simple Application Server console to connect to the Windows server.

    For more information, see Use the Simple Application Server console to connect to a Windows server.

  2. Open This PC. In the left-side navigation pane, right-click This PC and select Properties.
  3. In the left-side navigation pane of the System page, click Remote settings.
  4. In the Remote Desktop section of the System Properties dialog box, clear Allow connections only from computers running Remote Desktop with Network Level Authentication (recommended).
  5. Click Apply and then click OK.

    After the configurations are complete, you can try to connect to the server again.

What do I do if the "The remote session was disconnected because there are no Remote Desktop client access licenses available for this computer" message is prompted when I connect to a Windows server?

For information about how to solve this problem, see What do I do if the "The remote session was disconnected because there are no Remote Desktop client access licenses available for this computer" error message is prompted on the remote desktop of a Windows instance?

What do I do if I cannot connect to a Windows server and the server cannot access the Internet?

A possible cause of this problem is that network interface controllers (NICs) are disabled on the Windows server. In this example, Windows Server 2012 R2 64-bit is used to describe how to solve this problem.
  1. Use the Simple Application Server console to connect to the Windows server.

    For more information, see Use the Simple Application Server console to connect to a Windows server.

  2. In the lower-right corner of the desktop, right-click the Network icon network icon and select Open Network and Sharing Center.
  3. In the left-side navigation pane, click Change adapter settings.
  4. Find the disabled network, right-click the network, and then select Enable.
  5. After the network is enabled, right-click the network and select Properties.
  6. In the This connection uses the following items section, click Internet Protocol Version 4 (TCP/IPv4) and click Properties.
  7. On the General tab, click Obtain an IP address automatically, click Obtain DNS server address automatically, and then click OK.

    After the configurations are complete, you can try to connect to the server again.