Troubleshooting Steps to Fix Tomcat Issues

If your Tomcat server is running, but you cannot access it from your browser, several common issues could be causing this problem. Here are some steps to troubleshoot and resolve the issue:

Firewall Rules

Ensure that the firewall rules on your Google Cloud Platform (GCP) VM allow traffic on port 8080. You can check and create a firewall rule in the GCP console:

Go to the VM instance details page.
Ensure that "Allow HTTP traffic" and "Allow HTTPS traffic" checkboxes are selected.
If not, manually create a firewall rule to allow TCP traffic on port 8080. This can be done by navigating to the VPC network section and adding a firewall rule allowing ingress traffic on port 8080 from any IP address.
To check firewall rules list using gcloud SDK or CLI, type the following command:

gcloud compute firewall-rules list
To create the rule (if it isn't created) type the following command:

gcloud compute firewall-rules create allow-tomcat-8080 --allow tcp:8080 --target-tags tomcat-server --description="Allow traffic on port 8080 for Tomcat" --direction=INGRESS --priority=1000 --network=default
You can verify on the console as well:
Verify your tomcat service is running or not. Type the following command to test and check service should be Active:

systemctl status tomcat
Tomcat Configuration

Verify that Tomcat is configured to listen on the correct IP address and port. By default, Tomcat may only listen on localhost. Modify the server.xml file to ensure it listens on all interfaces:
- Edit the server.xml file located in the Tomcat conf directory.
- Ensure the Connector element for port 8080 looks like this
  
  <Connector port="8080" protocol="HTTP/1.1"
  
  connectionTimeout="20000"
  
  redirectPort="8443"
  
  address="0.0.0.0" />
- To check and edit the server.xml file in your Tomcat installation, follow these steps:
  
  SSH into your VM
- Connect to your Google Cloud Platform (GCP) VM instance using SSH.
  
  Navigate to the Tomcat Configuration Directory
- Change to the directory where Tomcat is installed. By default, this is usually /opt/tomcat.
  
  cd /opt/tomcat
  
  Locate the server.xml file
- The server.xml file is located in the conf directory inside your Tomcat installation directory
  
  cd conf
  
  Open the server.xml file for editing
- Use a text editor like nano or vim to open the server.xml file. For example, using vim:
  
  sudo vim server.xml
  
  Edit the server.xml file
- Look for the <Connector> element for port 8080 and ensure it is configured to listen on all IP addresses by setting the address attribute to 0.0.0.0.
  
  <Connector port="8080" protocol="HTTP/1.1"
  
  connectionTimeout="20000"
  
  redirectPort="8443"
  
  address="0.0.0.0" />
  
  Save and exit the editor
- If using nano, you can save the file by pressing Ctrl + O, then Enter, and exit by pressing Ctrl + X.
  
  Restart Tomcat
- After making changes to the server.xml file, restart the Tomcat service to apply the changes.
  
  sudo systemctl restart tomcat