telnet for port 5433 is not working while it works for port 22

Applications IP Networking
1

Hi,

I am trying to set up a dev environment and I have Ubuntu server (10.16.1.92) and a CentOS VM (10.16.3.235) on this. On the CentOS I have a program running on port 5433. Now my problem is that I am unable to telnet this port from another Windows server whereas I can telnet port 22 from Windows.
How can I enable port 5433 to be telnet(ed) from windows?

I am a developer and dont have much knowledge about resolving this issue.

I am giving below o/p of commands from CentOS VM:

[root@localhost ~]# netstat -apnt
Active Internet connections (servers and established)
Proto Recv-Q Send-Q Local Address               Foreign Address             State       PID/Program name  
tcp        0      0 0.0.0.0:22                  0.0.0.0:*                   LISTEN      1745/sshd               
tcp        0      0 0.0.0.0:5433                0.0.0.0:*                   LISTEN      2354/vertica       
tcp        0      0 :::5433                     :::*                        LISTEN      2354/vertica       

[root@localhost ~]# nmap -v -sV 10.16.3.235 -p 5433
..short o/p..
PORT     STATE SERVICE VERSION
5433/tcp open  pyrrho?

[root@localhost ~]# ss -aln
Recv-Q Send-Q                                   Local Address:Port                                     Peer Address:Port
0      128                                                 :::22                                                 :::*    
0      128                                                  *:22                                                  *:*    
0      128                                                 :::5433                                               :::*    
0      128                                                  *:5433                                                *:*

Thanks,
Rishav

2

Probably the iptables firewall. You have to add a rule for port 5433 (port 22 is open in the default configuration).

First have a look at the file /etc/sysconfig/iptables

# Firewall configuration written by system-config-firewall
# Manual customization of this file is not recommended.
*filter
:INPUT ACCEPT [0:0]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [0:0]
-A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
-A INPUT -p icmp -j ACCEPT
-A INPUT -i lo -j ACCEPT
-A INPUT -m state --state NEW -m tcp -p tcp --dport 22 -j ACCEPT
-A INPUT -m state --state NEW -m tcp -p tcp --dport 80 -j ACCEPT
-A INPUT -m state --state NEW -m tcp -p tcp --dport 19102 -j ACCEPT
-A INPUT -j REJECT --reject-with icmp-host-prohibited
-A FORWARD -j REJECT --reject-with icmp-host-prohibited
COMMIT

Now find a nice spot somewhere in between the existing accept rules

# Firewall configuration written by system-config-firewall
# Manual customization of this file is not recommended.
*filter
:INPUT ACCEPT [0:0]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [0:0]
-A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
-A INPUT -p icmp -j ACCEPT
-A INPUT -i lo -j ACCEPT
-A INPUT -m state --state NEW -m tcp -p tcp --dport 22 -j ACCEPT
-A INPUT -m state --state NEW -m tcp -p tcp --dport 80 -j ACCEPT
-A INPUT -m state --state NEW -m tcp -p tcp --dport 5433 -j ACCEPT
-A INPUT -m state --state NEW -m tcp -p tcp --dport 19102 -j ACCEPT
-A INPUT -j REJECT --reject-with icmp-host-prohibited
-A FORWARD -j REJECT --reject-with icmp-host-prohibited
COMMIT

Save your changes and restart the firewall:

service iptables restart
1 Like
3

Do you have an error message for us to analyse?

4

thanks @hergp will do the same and post the result.

@RudiC: I am not getting any error in Unix/CentOS side (and my application is also running fine on this box) but when i try to telnet port 5433 on this machine from a Windows box I am getting "Connection Refused" error.

5

btw, port 22 is ssh - telnet connects on port 23.
I'm surprised you can telnet to port 22 - I'd expect a "connection refused" (or similar) here as well. In your netstat listing you have the program "vertica" listening on port 5433. Are you sure it accepts telnet connections?
Did you try a telnet localhost 5433 on the unix side?

6

thanks a ton @hergp adding the lines and restarting the iptables resolved the issue :slight_smile:
@RudiC: now I am able to telnet 5433 from localhost as well as Windows machine.
Thanks a lot guys