Clients Can't Establish Connection

Learn how to troubleshoot client issues with connecting to HST Server.

Test SSH ports and HTTP/HTTPS ports.
1. On the client computer, run the following command:
```
# telnet server_ip_address port
```
  For example, to test connection to 10.0.1.1 through TCP/33001, you run the following command:
```
# telnet 10.0.1.1 33001
```
2. If the client cannot establish connections to the ports, verify the port number and the firewall configuration of HST Server. Also make sure that the client firewall allows outbound connections.
Test UDP ports.
If you can establish an SSH connection but not run a FASP file transfer, there might be a firewall blockage of FASP's UDP port.
Verify SSH service status
If there is no firewall blockage between the client and your HST Server, on the client machine, try establishing a SSH connection: (HST Server address: 10.0.1.1, TCP/33001)
```
# ssh aspera_user_1@10.0.1.1 -p 33001
```
If the SSH service runs normally, the client should see a message prompting to continue the connection or for a password. However, if you see a "Connection Refused" message, which indicates that the SSH service isn't running, review your SSH service status. Ignore the "permission denied" message after entering the password, which is discussed in next steps.
Applied authentication method is enabled in SSH
If you can establish a SSH connection, but it returns "permission denied" message, the SSH Server on your HST Server might have password authentication disabled:
```
Permission denied (publickey,keyboard-interactive).
```
Open your SSH Server configuration file with a text editor:
```
/etc/ssh/sshd_config
```
To allow public key authentication, add or uncomment the PubkeyAuthentication yes. To allow password authentication, add or uncomment PasswordAuthentication yes. Here is a configuration example:
```
...
PubkeyAuthentication yes
PasswordAuthentication yes
...
```
To activate your changes, restart the SSH server.
Restart the SSH server to apply new settings.
Restarting your SSH server does not affect currently connected users.
```
# systemctl restart sshd.service
```
or for Linux systems that use init.d:
```
# service sshd restart
```
Verify the Apache configuration.
If the client can access your HST Server through the HTTP or HTTPS port, but the client's browser cannot open the HST Server web UI (deprecated), there may be configuration problems. See Configuring the Apache Server to Host the HST Server Web UI and review the configuration.
Verify that the user credentials are correct, and the user has sufficient access permissions to their docroot
1. Attempt to establish an SSH connection:
```
# ssh username@server_ip_address -p  port
```
  For example:
```
$ ssh aspera_user_1@10.0.1.1 -p 33001
```
2. Enter the user's password.
  If you see "Permission denied" message, you may have a wrong user credentials, or the user doesn't have sufficient access permissions to its docroot.
Verify that the user is set up for web UI (deprecated) authentication
HST Server uses Apache's authentication to authorize web UI access. If the client can establish SSH connections, but cannot authenticate to the web UI, the user account might not be configured for web UI correctly. To do so, run the following command:
```
$ htpasswd /opt/aspera/etc/webpasswd username
```
Important: Use the -c option ONLY if this is the first time running htpasswd to create the webpasswd file. Do not use the -c option otherwise.