Can't open port 8080 on Google Compute Engine running Debian

Question

I am trying to run a simple Python http server that displays "hello world" on port 8080 using a micro instance. I also have 4 instances of Tornado running behind Nginx. Connecting to Nginx/Tornado on port 80 is not a problem.

I have added port 8080 to my firewall settings, and ensured port 8080 is open and listening on the server but no matter what I do, my connection is always refused. I have tried connecting using browsers, telnet and wget and every single connection is refused.

Here is the output of netstat -an | grep "LISTEN "

tcp        0      0 0.0.0.0:8000            0.0.0.0:*               LISTEN tcp        0      0 0.0.0.0:8001            0.0.0.0:*               LISTEN tcp        0      0 0.0.0.0:8002            0.0.0.0:*               LISTEN tcp        0      0 0.0.0.0:8003            0.0.0.0:*               LISTEN tcp        0      0 0.0.0.0:8080            0.0.0.0:*               LISTEN tcp        0      0 0.0.0.0:80              0.0.0.0:*               LISTEN tcp        0      0 0.0.0.0:22              0.0.0.0:*               LISTEN tcp6       0      0 :::8000                 :::*                    LISTEN tcp6       0      0 :::8001                 :::*                    LISTEN tcp6       0      0 :::8002                 :::*                    LISTEN tcp6       0      0 :::8003                 :::*                    LISTEN tcp6       0      0 :::22                   :::*                    LISTEN 

Here is my iptables list

Chain INPUT (policy ACCEPT) target     prot opt source               destination ACCEPT     tcp  --  anywhere             anywhere             tcp dpt:http-alt  Chain FORWARD (policy ACCEPT) target     prot opt source               destination  Chain OUTPUT (policy ACCEPT) target     prot opt source               destination 

Here is the Python script I am using:

#!/usr/bin/python from BaseHTTPServer import BaseHTTPRequestHandler,HTTPServer  PORT_NUMBER = 8080  #This class will handles any incoming request from #the browser class myHandler(BaseHTTPRequestHandler):     #Handler for the GET requests    def do_GET(self):       self.send_response(200)       self.send_header('Content-type','text/html')       self.end_headers()       # Send the html message       self.wfile.write("Hello World!")       return  try:    #Create a web server and define the handler to manage the    #incoming request    server = HTTPServer(('', PORT_NUMBER), myHandler)    print 'Started httpserver on port ' , PORT_NUMBER     #Wait forever for incoming htto requests    server.serve_forever()  except KeyboardInterrupt:    print '^C received, shutting down the web server'    server.socket.close() 

Answer 1

Does your network have the corresponding firewall rule? Follow the next steps to create it.

1. Go to the Developers Console and click on the corresponding project.

2. Click on 'Compute'

3. Click on 'Networks'

4. Click on the name of the corresponding network. You can see in which network is your instance clicking on 'VM instances' under the 'Compute Engine' section or with the command:

   gcloud compute instances describe <instance> | grep "network:" | awk -F/ '{print $(NF)}'

5. Under the Firewall rules section, click 'Create new'

6. Enter a name for the firewall rule and in the field 'Protocols & ports' type: tcp:8080

7. Save the rule

After that, you should be able to access your HTTP server.

Otherwise you can try to see if your machine receives the SYN TCP packets in that port with the command: sudo tcpdump -i eth0 port 8080

Hope it helps