12/100 Linux Network Services
Our monitoring tool has reported an issue in Stratos Datacenter. One of our app servers has an issue, as its Apache service is not reachable on port 8084 (which is the Apache port). The service itself could be down, the firewall could be at fault, or something else could be causing the issue. Use tools like telnet, netstat, etc. to find and fix the issue. Also make sure Apache is reachable from the jump host without compromising any security settings.
Once fixed, you can test the same using command curl http://stapp01:8084 command from jump host.
#Determine which app is not responding using telnet from jump host
telnet stapp01 8084
Trying 172.16.238.10...
telnet: connect to address 172.16.238.10: No route to host
ssh tony@172.16.238.10 or ssh tony@stapp01
sudo systemctl status httpd
httpd.service - The Apache HTTP Server
Loaded: loaded (/usr/lib/systemd/system/httpd.service; disabled; vendor preset: disabled)
Active: failed (Result: exit-code) since Wed 2025-09-03 10:53:38 UTC; 7min ago
Sep 03 10:53:38 stapp01.stratos.xfusioncorp.com httpd[504]: (98)Address already in use: AH00072: make_sock: coul
d not bind to address 0.0.0.0:8084
# Check ports with netsta
sudo netstat -tulpn | grep 8084
tcp 0 0 127.0.0.1:8084 0.0.0.0:* LISTEN 443/sendmail: accep
# Kill the process running - which as shown above is 443
sudo kill 443
sudo netstat -tulpn # Check to ensure it has been removed
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name
tcp 0 0 127.0.0.11:37793 0.0.0.0:* LISTEN -
tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN 315/sshd
tcp6 0 0 :::22 :::* LISTEN 315/sshd
udp 0 0 127.0.0.11:39378 0.0.0.0:* -
sudo systemctl restart httpd
curl http://stapp01:8084Lab died during 1st attempt so port changed to 5003. Curl is showing the contents of the webapp however you need to verify that you can also reach this from the jump host - which still shows as no route to host - as shown below
telnet stapp01 5003
Trying 172.16.238.10...
telnet: connect to address 172.16.238.10: No route to host#Back on stapp01
sudo iptables -L -n
Chain INPUT (policy ACCEPT)
target prot opt source destination
ACCEPT all -- 0.0.0.0/0 0.0.0.0/0 state RELATED,ESTABLISHED
ACCEPT icmp -- 0.0.0.0/0 0.0.0.0/0
ACCEPT all -- 0.0.0.0/0 0.0.0.0/0
ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 state NEW tcp dpt:22
REJECT all -- 0.0.0.0/0 0.0.0.0/0 reject-with icmp-host-prohibited
Chain FORWARD (policy ACCEPT)
target prot opt source destination
REJECT all -- 0.0.0.0/0 0.0.0.0/0 reject-with icmp-host-prohibited
Chain OUTPUT (policy ACCEPT)
target prot opt source destinationWithin Chain INPUT (policy ACCEPT) there is no rule allowing for TCP port 5003, so the last REJECT rule applies. To open port 5003 use:
sudo iptables -I INPUT 5 -p tcp --dport 5003 -j ACCEPT
sudo service iptables saveNote INPUT 5 puts the new rule above REJECT assuming that REJECT is the 5th rule in the chain.
Finally, back on the jump host - use telnet to check the connection:
telnet stapp01 5003
Trying 172.16.238.10...
Connected to stapp01.
curl http://stapp01:5003