Port can't open on Ubuntu 16.04

Question

I have a Ubuntu 16 installed on a Hetzner's VPS. I want to open port 11121 which I did it several times before on other VPSs.

I've tried ufw & iptables but when I check, I see the port is still closed!

Hint: The only thing that happened for this VPS but not the previous one, was a checkmark for RDNS on Hetzner management panel, then I've typed the reversed public IP on a textbox and saved. But I wasn't sure about this and I deleted it again. The only thing that I guess is this action and its effect on NAT configs.

Even I entered allow command via iptables but it returned below status after that:

    #iptables -L -nv
Chain INPUT (policy ACCEPT 10248 packets, 4165K bytes)
 pkts bytes target     prot opt in     out     source               destination         

Chain FORWARD (policy ACCEPT 0 packets, 0 bytes)
 pkts bytes target     prot opt in     out     source               destination         

Chain OUTPUT (policy ACCEPT 10260 packets, 4288K bytes)
 pkts bytes target     prot opt in     out     source               destination

Then I installed UFW and I tried to open some ports manually, then enable the UFW and below is the status:

# ufw status
Status: active

To                         Action      From
--                         ------      ----
11121                      ALLOW       Anywhere                  
22                         ALLOW       Anywhere                  
80                         ALLOW       Anywhere                  
443                        ALLOW       Anywhere                  
11121 (v6)                 ALLOW       Anywhere (v6)             
22 (v6)                    ALLOW       Anywhere (v6)             
80 (v6)                    ALLOW       Anywhere (v6)             
443 (v6)                   ALLOW       Anywhere (v6)      

and the status of iptables is showing as below now:

# iptables -S
-P INPUT DROP
-P FORWARD DROP
-P OUTPUT ACCEPT
-N ufw-after-forward
-N ufw-after-input
-N ufw-after-logging-forward
-N ufw-after-logging-input
-N ufw-after-logging-output
-N ufw-after-output
-N ufw-before-forward
-N ufw-before-input
-N ufw-before-logging-forward
-N ufw-before-logging-input
-N ufw-before-logging-output
-N ufw-before-output
-N ufw-logging-allow
-N ufw-logging-deny
-N ufw-not-local
-N ufw-reject-forward
-N ufw-reject-input
-N ufw-reject-output
-N ufw-skip-to-policy-forward
-N ufw-skip-to-policy-input
-N ufw-skip-to-policy-output
-N ufw-track-forward
-N ufw-track-input
-N ufw-track-output
-N ufw-user-forward
-N ufw-user-input
-N ufw-user-limit
-N ufw-user-limit-accept
-N ufw-user-logging-forward
-N ufw-user-logging-input
-N ufw-user-logging-output
-N ufw-user-output
-A INPUT -j ufw-before-logging-input
-A INPUT -j ufw-before-input
-A INPUT -j ufw-after-input
-A INPUT -j ufw-after-logging-input
-A INPUT -j ufw-reject-input
-A INPUT -j ufw-track-input
-A FORWARD -j ufw-before-logging-forward
-A FORWARD -j ufw-before-forward
-A FORWARD -j ufw-after-forward
-A FORWARD -j ufw-after-logging-forward
-A FORWARD -j ufw-reject-forward
-A FORWARD -j ufw-track-forward
-A OUTPUT -j ufw-before-logging-output
-A OUTPUT -j ufw-before-output
-A OUTPUT -j ufw-after-output
-A OUTPUT -j ufw-after-logging-output
-A OUTPUT -j ufw-reject-output
-A OUTPUT -j ufw-track-output
-A ufw-after-input -p udp -m udp --dport 137 -j ufw-skip-to-policy-input
-A ufw-after-input -p udp -m udp --dport 138 -j ufw-skip-to-policy-input
-A ufw-after-input -p tcp -m tcp --dport 139 -j ufw-skip-to-policy-input
-A ufw-after-input -p tcp -m tcp --dport 445 -j ufw-skip-to-policy-input
-A ufw-after-input -p udp -m udp --dport 67 -j ufw-skip-to-policy-input
-A ufw-after-input -p udp -m udp --dport 68 -j ufw-skip-to-policy-input
-A ufw-after-input -m addrtype --dst-type BROADCAST -j ufw-skip-to-policy-input
-A ufw-after-logging-forward -m limit --limit 3/min --limit-burst 10 -j LOG --log-prefix "[UFW BLOCK] "
-A ufw-after-logging-input -m limit --limit 3/min --limit-burst 10 -j LOG --log-prefix "[UFW BLOCK] "
-A ufw-before-forward -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT
-A ufw-before-forward -p icmp -m icmp --icmp-type 3 -j ACCEPT
-A ufw-before-forward -p icmp -m icmp --icmp-type 4 -j ACCEPT
-A ufw-before-forward -p icmp -m icmp --icmp-type 11 -j ACCEPT
-A ufw-before-forward -p icmp -m icmp --icmp-type 12 -j ACCEPT
-A ufw-before-forward -p icmp -m icmp --icmp-type 8 -j ACCEPT
-A ufw-before-forward -j ufw-user-forward
-A ufw-before-input -i lo -j ACCEPT
-A ufw-before-input -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT
-A ufw-before-input -m conntrack --ctstate INVALID -j ufw-logging-deny
-A ufw-before-input -m conntrack --ctstate INVALID -j DROP
-A ufw-before-input -p icmp -m icmp --icmp-type 3 -j ACCEPT
-A ufw-before-input -p icmp -m icmp --icmp-type 4 -j ACCEPT
-A ufw-before-input -p icmp -m icmp --icmp-type 11 -j ACCEPT
-A ufw-before-input -p icmp -m icmp --icmp-type 12 -j ACCEPT
-A ufw-before-input -p icmp -m icmp --icmp-type 8 -j ACCEPT
-A ufw-before-input -p udp -m udp --sport 67 --dport 68 -j ACCEPT
-A ufw-before-input -j ufw-not-local
-A ufw-before-input -d 224.0.0.251/32 -p udp -m udp --dport 5353 -j ACCEPT
-A ufw-before-input -d 239.255.255.250/32 -p udp -m udp --dport 1900 -j ACCEPT
-A ufw-before-input -j ufw-user-input
-A ufw-before-output -o lo -j ACCEPT
-A ufw-before-output -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT
-A ufw-before-output -j ufw-user-output
-A ufw-logging-allow -m limit --limit 3/min --limit-burst 10 -j LOG --log-prefix "[UFW ALLOW] "
-A ufw-logging-deny -m conntrack --ctstate INVALID -m limit --limit 3/min --limit-burst 10 -j RETURN
-A ufw-logging-deny -m limit --limit 3/min --limit-burst 10 -j LOG --log-prefix "[UFW BLOCK] "
-A ufw-not-local -m addrtype --dst-type LOCAL -j RETURN
-A ufw-not-local -m addrtype --dst-type MULTICAST -j RETURN
-A ufw-not-local -m addrtype --dst-type BROADCAST -j RETURN
-A ufw-not-local -m limit --limit 3/min --limit-burst 10 -j ufw-logging-deny
-A ufw-not-local -j DROP
-A ufw-skip-to-policy-forward -j DROP
-A ufw-skip-to-policy-input -j DROP
-A ufw-skip-to-policy-output -j ACCEPT
-A ufw-track-output -p tcp -m conntrack --ctstate NEW -j ACCEPT
-A ufw-track-output -p udp -m conntrack --ctstate NEW -j ACCEPT
-A ufw-user-input -p tcp -m tcp --dport 11121 -j ACCEPT
-A ufw-user-input -p udp -m udp --dport 11121 -j ACCEPT
-A ufw-user-input -p tcp -m tcp --dport 22 -j ACCEPT
-A ufw-user-input -p udp -m udp --dport 22 -j ACCEPT
-A ufw-user-input -p tcp -m tcp --dport 80 -j ACCEPT
-A ufw-user-input -p udp -m udp --dport 80 -j ACCEPT
-A ufw-user-input -p tcp -m tcp --dport 443 -j ACCEPT
-A ufw-user-input -p udp -m udp --dport 443 -j ACCEPT
-A ufw-user-limit -m limit --limit 3/min -j LOG --log-prefix "[UFW LIMIT BLOCK] "
-A ufw-user-limit -j REJECT --reject-with icmp-port-unreachable
-A ufw-user-limit-accept -j ACCEPT

Edit:

# netstat -tanp
Active Internet connections (servers and established)
Proto Recv-Q Send-Q Local Address           Foreign Address         State       PID/Program name
tcp        0      0 127.0.0.1:3306          0.0.0.0:*               LISTEN      1121/mysqld     
tcp        0      0 127.0.0.1:6379          0.0.0.0:*               LISTEN      1127/redis-server 1
tcp        0      0 0.0.0.0:22              0.0.0.0:*               LISTEN      1096/sshd       
tcp        0    332 172.31.1.100:22         5.116.231.153:28282     ESTABLISHED 7506/0          
tcp6       0      0 :::443                  :::*                    LISTEN      1158/apache2    
tcp6       0      0 :::80                   :::*                    LISTEN      1158/apache2    
tcp6       0      0 :::22                   :::*                    LISTEN      1096/sshd       
tcp6       0      0 172.31.1.100:80         155.94.88.138:54138     TIME_WAIT   -       

Solution

In my case, the issue was not running the service on the port. Actually the port was not listening with any application or service.

As you see in following output of netstat -tanp, there was no port on listening:

# netstat -tanp
Active Internet connections (servers and established)
Proto Recv-Q Send-Q Local Address           Foreign Address         State       PID/Program name
tcp        0      0 127.0.0.1:3306          0.0.0.0:*               LISTEN      1121/mysqld     
tcp        0      0 127.0.0.1:6379          0.0.0.0:*               LISTEN      1127/redis-server 1
tcp        0      0 0.0.0.0:22              0.0.0.0:*               LISTEN      1096/sshd       
tcp        0    332 172.31.1.100:22         5.116.231.153:28282     ESTABLISHED 7506/0          
tcp6       0      0 :::443                  :::*                    LISTEN      1158/apache2    
tcp6       0      0 :::80                   :::*                    LISTEN      1158/apache2    
tcp6       0      0 :::22                   :::*                    LISTEN      1096/sshd       
tcp6       0      0 172.31.1.100:80         155.94.88.138:54138     TIME_WAIT   -       

I didn't consider this fact, because I believed the service is running as usual and I've got no errors!

Special thanks to Michael Hampton & Nasir Riley for their helpful comments under the question.

Comments

[Admin]

@MichaelHampton thx Michael but I've installed Shadowsocks and it's running. Does it mean that is not working correctly?!

[Admin]

Your own netstat output shows that nothing is listening on port 11121, and nothing named shadowsocks (or anything similar) is listening to any port.

[Admin]

@MichaelHampton so it's necessary to run something on a port, then we can find it Open from outside, right?

[Admin]

Yes. Your rules show that connections are allowed on port 11121 but it is necessary to have an application or service listening on it. After that, you will see the port appear when you run netstat -tanp.

[Admin]

Guys, thanks you so much, you were right. My services is not running!! No I have to looking for another solution

[Admin]

Please don't put "SOLVED" or answers into the question. They belong below, as an answer.

[Admin]

@MichaelHampton you're right. But I didn't want to post your answers as mine and leave the topic without clear answer.

[Admin]

You may happily write your own answers here. I have plenty of reputation points and I don't need many more :)