Table of Contents
21 Networking
Firewall Configuration
ini Settings
server.tcp.paranoid
server.tcp.paranoid = True/False
When TRUE, this token configures LabVIEW to accept VI Server TCP connections only from localhost, regardless of the 'Machine Access' list configuration in Tools > Options > VI Server. In other words, all remote network connection attempts to VI Server are denied.
When FALSE, this token configures VI Server to operate normally.
Source: dnatt
Pitfalls
IP to String
The IP to String function converts an IP network address to a string.
The dot notation? input indicates whether name is in dot-notation format. The default is FALSE, which makes LabVIEW try to resolve the name. This can take a long time depending on the specific DNS setup of the computer this function is executed on.
To avoid timeouts, if a resolved name is not required, make sure to wire a true constant to the dot notation? input of this function.
TCP Listen - DNS Resolution
The same tip about disabling DNS resolution (as described above) applies to TCP Listen.vi, too. If a resolved name is not required, make sure to wire a false constant to the Resolve remote address? input.
Also, whenever TCP Listen receives and spawns a new connection, any existing connections will see a short period of being blocked - you can read more at:
TCP TIME-WAIT
Why Do I Get Error 60 When Closing and Opening a TCP Connection on the Same Local Port?
Nagle Algorithm
By default, LabVIEW uses the Nagle algorithm when doing TCP communication.
The Nagle algorithm is one of the basic algorithms of TCP that helps reduce Internet traffic by combining several small packets into a single large one. While this increases the efficiency of sending large messages such as those commonly sent in normal Internet traffic, the algorithm can introduce some latency for situations where small amounts of information are being sent back and forth, such as in instrument handshaking.
Connection Limit Exceeded
If you encounter “Error 128 (0x80) Open Connection Limit Exceeded in LabVIEW”, this is due to a limitation of connections that can be created. The LabVIEW User Manual explicitly states: “You can create up to 1024 TCP connections on a single port.”
In practice, that shows up as Error 128 (Open connection limit exceeded) once your process has ~1024 active LabVIEW TCP connection refnums (and often “a little less” because LabVIEW and/or your app may already have a few sockets open for other things).