Cannot access Simple Application Server from a specific IP address

Symptoms

You cannot connect to an Alibaba Cloud simple application server from a specific IP address. For example, after you deploy a BT panel on a simple application server, if the server's firewall blocks port 8888, your browser displays a "This site can't be reached" message when you try to access the panel.

The browser displays the error code ERR_CONNECTION_TIMED_OUT, which indicates that the destination IP address took too long to respond.

Causes

This issue may be caused by the following:

• A required port is closed or disabled.

• Access is limited to specific CIDR blocks.

Solutions

Choose the appropriate solution based on your scenario.

Solution 1: Check for disabled ports

Your simple application server's firewall may be blocking the target port. By default, the firewall allows traffic on ports 22 (SSH), 80 (HTTP), and 443 (HTTPS), and denies all other ports. For more information, see Manage firewalls.

Solution 2: Check for CIDR block restrictions

1. Navigate to the Firewall page of your simple application server. For more information, see Manage firewalls.

2. On the Firewall page, in the IP Source to be Used column for the relevant port, check if your source IP address is included in the allowed CIDR block.

3. If your source IP address is not included in the allowed CIDR block, click Modify.

4. In the Modify dialog box, update the CIDR block to include your source IP address.

5. Click OK.

Solution 3: Check for IP blocks by Security Center

1. Use Security Center to run a security scan on your server. For more information, see Quick start.

2. If Security Center is blocking your IP address, submit a ticket to have it unblocked.