TCP Create Listener Function

LabVIEW 2018 Help

Edition Date: March 2018
Part Number: 371361R-01
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Owning Palette: TCP VI and Functions

Requires: Base Development System

Creates a listener for a TCP network connection. Wire 0 to the port input to dynamically choose an available TCP port the operating system determines is valid for use. Use the TCP Open Connection to query the NI Service Locator for the port number registered with the service name.


net address specifies on which network address to listen. Specifying an address is useful if you have more than one network card, such as two Ethernet cards, and want to listen only on the card with the specified address. If you do not specify a network address, LabVIEW listens on all network addresses. Use the String To IP function to obtain the IP network address of the current computer.
service name creates a known reference for the port number. If you specify a service name, LabVIEW registers the service name and the port number with the NI Service Locator.
port is the port number on which you want to listen for a connection.
timeout ms specifies the time, in milliseconds, that the function waits before the function completes and returns an error. The default value is 25,000 ms or 25 seconds. A value of -1 indicates to wait indefinitely.
error in describes error conditions that occur before this node runs. This input provides standard error in functionality.
listener ID is a network connection refnum that uniquely identifies the listener.
port returns the port number the function used. If the input port is not zero, the output port number equals the input port number. Wire 0 to the port input to dynamically choose an available TCP port the operating system determines is valid for use. As defined by the Internet Assigned Numbers Authority (IANA), valid port numbers are between the range of 49152 through 65535. Well Known Ports are between the range of 0 through 1023 and Registered Ports are between the range of 1024 through 49151. Not all operating systems follow the IANA standard; for example, Windows returns dynamic ports between the range of 1024 through 5000.
error out contains error information. This output provides standard error out functionality.


Refer to the TCP Named Service.lvproj in the labview\examples\Data Communication\Protocols\TCP\TCP Named Service directory for an example of using the TCP Create Listener function.


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