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Question I can PING and Telnet NPort, but why can not my own TCP Client program successfully connect with NPort?
Question Type Application
Updated 4/1/2008 3:40:01 PM
Hits 21491
Products NPort 5230 Series,NPort Express DE-211,NPort Express DE-311,NPort 5210/NPort 5230/NPort 5232 Series,NPort 5410/NPort 5430/NPort 5450 Series,NPort 5430 Series,NPort 5610/NPort 5630 Series,NE-4100T,NE-4110S,NE-4110A,NE-4120S,NE-4120A,NPort Server Lite DE-301/302/304/331/332/334



1. Improper operation mode.

2. NPort's listening TCP port is not correct.

3. DHCP issue.

4. Improper DIP switch settings on DE-311/211.

5. NPort is occupied.

6. Access right authentication.

7. Firewall filtering rules.


  • Your operation mode must be [TCP Server mode].
  • The NPort's listening TCP Port must match your own TCP Client program.
  • If your Host and NPort are in a DHCP environment :
    a) You must assign a fixed IP address to NPort & your Host.
    b) Under a DHCP environment, you can map a specific IP address to your NPort's & Host's MAC address.
  • The DE-311/211's DIP SW1 must be OFF for data communication.
  • Telnet NPort's IP address, and check the ''Conn. Status'' message under [Monitor]. It must be set to ''listen'' before executing your program .
  • a)NPort Server Pro/Lite/Express:check if [Desti.IP] column is proper.
    b)NPort 5210/5230/5410/5430/5430I/5610-8/5610-16:check if [Accessible IP Settings] is proper.
  • Make sure that your firewall can open the listening TCP port.

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