Firewall between Client and Server - Which ports do you open?

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I want to know the following: (exam type question)

When you have a client-server system, that uses uncommon ports (e.g. in range 48000 - 49000), and you have a firewall between the client and the server, which ports do you need to open on this firewall? Here are the options:

  • You need to open ports for communication from the client to the server
  • You need to open ports for communication from the server to the client
  • You need to open ports for communication from the server to the client and from the client to the server
  • No need to open any ports

NOTE: The traffic between the Server and the Client application is TCP/IP and is socket-based.

What would be the correct answer here?

DextrousDave

Posted 2013-10-20T12:36:59.437

Reputation: 385

1The question is too vague to answer. Is the firewall stateful or stateless? Is the system using TCP, UDP, or both? You can only answer by making all kinds of guesses. – David Schwartz – 2013-10-20T13:08:32.220

This is actually a question from an Exam, and the only thing I replaced was the name of the server and client software...So I do not know if it is stateful or stateless – DextrousDave – 2013-10-20T14:12:11.517

Answers

1

Assuming the server is not behind a NAT, the option "You need to open ports for communication from the client to the server" would be correct. Meaning you have to open the ports server side. Understand a firewall exactly as a wall. If there is a wall serverside, the clients cannot communicate with the server. That said, you have to "remove" this wall for your specific port.

Doon

Posted 2013-10-20T12:36:59.437

Reputation: 150

2What if the firewall is stateless? How will the server communicate with the client? – David Schwartz – 2013-10-20T13:08:57.563

thank you Doon. Appreciate your answer. This is actually a question from an Exam, and the only thing I replaced was the name of the server and client software...So I do not know if it is stateful or stateless – DextrousDave – 2013-10-20T13:55:58.663

Asked: 2013-10-20T12:36:59.437

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Active: 2013-10-20T18:23:54.927