How are TCP/IP port numbers assigned?

HCL Domino Domino Forum
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I am being asked to describe the assignment of a TCP/IP port number when a notes client connects to the notes server. Is the number assigned by the server or the client. Also, is the connection single or bidirectional. What is the range of port numbers, 1024 - 5000? Can the range be controlled?

Thank you.

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Subject: How are TCP/IP port numbers assigned?

Hi, I’m not sure of what are you trying to do but if it helps, Domino uses a couple of TCP/IP ports that normally are related to a specific service. for example:

Port Service

25 SMTP

110 POP3

80 HTTP

443 HTTPS

1352 NRPC (this protocol is used between Notes Client and a Domino Server)

regards,

.::AleX::.

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Subject: RE: How are TCP/IP port numbers assigned?

I think he is talking about the port number assigend to each user which you can see through the admin client (notes users - port column).

I would like to know this as well. Please post it when you find out.

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Subject: It is random …

according to a technote I found in the knowledge base, it is random:

Port numbers in the range 1 - 1024 are called reserved ports because they are reserved for well-known system services. The TCP software never uses reserved ports when it must select a client-side port number at random. Rather, it selects at random a number from a range above 1024 called the ephemeral port range. The Internet authority uses the low-end range above 1024 to assign port numbers to registered applications such as Lotus Notes/Domino’s NRPC services, which use 1352.

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Subject: RE: It is random …

Paul,I know about 1352 but not the randomness of assignments. Thanks for explaining.

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Subject: RE: It is random …

In speaking with IBM tech support I was given the following info:

The OS on the client computer, using the network software, randomly assigns a TCP/IP port number with which to connect to the OS on the Notes server. The OS on the server then recognizes that the client is using NRPC and routes it through port 1352 to the notes server. The randomly assigned port numbers are from the client side OS and not from the server OS or the Domino server.

Thank You

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Subject: RE: It is random …

Thanks for your infor. Back to your question, is there any way to control the port number on client side? Is it possible to limit the client to used only one port number to communicate with the server?

Hope you got the answer for this. Thanks.