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Resolving SMSC Communication Failures Due to Port and Firewall Issues

Overview

The issue was characterized by the error "Sep 7 12:47:12 XXXXX-MGR-01 snmptrapd[990]: 12:47:12 TRAP6.TEXTPASS-FXFER-MIB::serverSessionStopped TEXTPASS-FXFER-MIB::fxferClientIpAddress.0 = IpAddress: 10.28.20.228 TEXTPASS-ECI-GEN-MIB::eci# = STRING: FXFER from localhost", indicating a communication failure with the SMSC testing environment. This was due to no services listening on ports 2775 and 1035 and the firewall not allowing traffic on these ports. The issue was resolved by starting the iptables service and configuring it to start on boot.

Information

Error Message: "Sep 7 12:47:12 XXXXXX-MGR-01 snmptrapd[990]: 12:47:12 TRAP6.TEXTPASS-FXFER-MIB::serverSessionStopped TEXTPASS-FXFER-MIB::fxferClientIpAddress.0 = IpAddress: 10.28.20.228 TEXTPASS-ECI-GEN-MIB::eci# = STRING: FXFER from localhost"

Cause: The issue was caused by the absence of services listening on the required ports (2775 and 1035) and the firewall configuration not allowing traffic on these ports.

Resolution Steps:

  1. Verify Service Listening:
    • Run ss -lntp | egrep ':2775|:1035' to check if any services are listening on the required ports.
    • If no services are listening, ensure that the relevant application services are started.
  2. Update Firewall Configuration:
    • Check the current firewall status with sudo firewall-cmd --list-all.
    • Add the required ports to the firewall: 
      sudo firewall-cmd --zone=public --add-port=2775/tcp --permanent
sudo firewall-cmd --zone=public --add-port=1035/tcp --permanent
sudo firewall-cmd --reload
  3. Start iptables Service: 
    • If iptables is not running, start it manually with sudo systemctl start iptables.
    • Enable iptables to start on boot with sudo systemctl enable iptables.
  4. Verify Configuration: 
    • Confirm that the services are now listening on the required ports using ss -lntp | egrep ':2775|:1035'.
    • Test connectivity from a remote system using telnet <SMSC_IP> 2775 and telnet <SMSC_IP> 1035.

Note: If issues persist, check application logs for errors related to port binding or listener configuration.

Frequently Asked Questions

How do I check if a service is listening on a specific port?
Use the command ss -lntp | egrep ':<port_number>' to check if a service is listening on a specific port.
How can I ensure iptables starts automatically on boot?
Run sudo systemctl enable iptables to configure iptables to start automatically on boot.
What should I do if the service is not listening on the required ports after starting?
Check the application configuration files to ensure the correct ports are specified, and review logs for any errors related to port binding.
How can I verify the firewall configuration?
Use sudo firewall-cmd --list-all to view the current firewall configuration and ensure the required ports are open.
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  1. Mohammed Amer

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