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What Does the Local Port Input Parameter Mean in the InetTelnetOpen Function In CVI 7.1?

Primary Software: LabWindows/CVI Development Systems>>Full Development System
Primary Software Version: 7.1
Primary Software Fixed Version: N/A
Secondary Software: N/A

Problem: The local port parameter for the InetTelnetOpen function in CVI 7.1 is supposed to specify a port for telnet communication. I know that the normal port for the telnet server is 23, but what does the local port specify?

Solution: Well-known and registered port numbers are needed for server processes since a client must know the server’s port number to initiate contact. Hence, it is convention that most telnet servers use a default of port 23. In contrast, client processes can use any port number. Each time a client process initiates TCP communication it is assigned a temporary, or ephemeral, port number to use for that conversation. These port numbers are assigned in a pseudo-random way, since the exact number used is not important, as long as each process has a different number.

For the InetTelnetOpen function, assigning the local port to 0 will allow the TCP/IP software to assign an available ephemeral port number to the process.

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Report Date: 07/12/2005
Last Updated: 07/14/2005
Document ID: 3NBGMU8M

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