Is there a way to synchronize phonebooks between PnonerLite softphones, installed on different computers on my network? I can make PhonerLite to use phonebook.csv, stored on network share (by creating a symlink to it in folder, where phonebook is stored), but i have noticed, that when i close program? it saves phonebook, and when i close 4 clients on 4 PCs, only changes, that were made in LAST closed PhonerLite, are in file. Other are simply rewritten. As far i see now only one way  - give only one user read/write permissions to share with phonebook and make all changes on it. Is there any option to change the behavior of program: 1) make it to just add a string into phonebook in realtime (and read it on othe PC without restart); 2) or make it store contacts in some database (SQL etc), as an option?

So... If anyone needs it, i found solution:

1) Make a network share on your server and make sure all client PCs have R\W access to it;
2) Copy your phonebook.csv file to network share with names for each client - client1.csv, client2.csv, client3,csv etc.;
3) On each PC make a symlink to phonebook.csv file in network folder -DELETE file phonebook.txt in your program or AppData folder, then open CMD and execute a command - mklink /H "c:\PhonerLite\phonebook.csv" "\\SERVER\RealPhonebook\client1.csv" (replace paths with correct for your case);
4) Make sure your client reads phonebook file correctly;
5) Create on server in folder, where your phonebooks are stored batch and vbs files for merge, deduplicate merged results and make all phonebooks equal:

sync.bat: (merges all files)
@echo off
type nul > temp.csv
type nul > sync.csv,
copy *.csv temp.csv
for /f "delims=" %%I in (temp.csv) do findstr /X /C:"%%I" sync.csv >NUL ||(echo;%%I)>>sync.csv
del temp.csv
exit

cleanfile.vbs (Removes SUB simbol at the end of merged file, i am ukrainian, maybe it appears because of ukrainian names in phonebook)

Dim objFS, objFile, strPath, arrTemp
strPath = "sync.csv"
Set objFS = CreateObject("Scripting.FileSystemObject")
If objFS.FileExists(strPath) Then
    Set objFile = objFS.OpenTextFile(strPath, 1)
    arrTemp = Split(objFile.ReadAll, vbNewLine)
    objFile.Close
    For i = 0 To UBound(arrTemp)
        If InStr(1, arrTemp(i), "
", vbTextCompare) > 0 Then arrTemp(i) = Replace(arrTemp(i), "
", "")
    Next
    Set objFile = objFS.CreateTextFile(strPath, True)
    objFile.Write Join(arrTemp, vbNewLine)
    objFile.Close
    Set objFile = Nothing
End If
Set objFS = Nothing
WScript.Quit 0

deduplicate.bat (removes duplicate lines from merged file)

@echo off
setlocal disableDelayedExpansion
set "file=sync.csv"
set "line=%file%.line"
set "deduped=result.csv"
:efine a variable containing a linefeed character
set LF=^


::The 2 blank lines above are critical, do not remove
>"%deduped%" (
  for /f usebackq^ eol^=^%LF%%LF%^ delims^= %%A in ("sync.csv") do (
    set "ln=%%A"
    setlocal enableDelayedExpansion
    >"%line%" (echo !ln:\=\\!)
    >nul findstr /xlg:"%line%" "%deduped%" || (echo !ln!)
    endlocal
  )
)
>nul move /y "%deduped%" "ready.csv"
2>nul del "%line%"
exit

clean.bat (removes temp files and replaces all your phonebooks witn deduplicated merged file, i made also a backup option to folder backup)

@echo off
copy client*.csv D:\mergetest\csv\backup
copy ready.csv client1.csv
copy ready.csv client2.csv
copy ready.csv client3.csv
del sync.csv
copy ready.csv D:\mergetest\csv\backup
del ready.csv
exit

makephonebook.bat (main bat file, that launches all processes)

@ECHO OFF
START "" sync.bat
ping 127.0.0.1 -n 10 >nul
start /w wscript.exe  "cleanfile.vbs"
ping 127.0.0.1 -n 10 >nul
START "" deduplicate.bat
ping 127.0.0.1 -n 10 >nul
START "" clean.bat
exit

6) On server add makephonebook.bat to tasks list WHEN ALL YOUR CLIENTS ARE NOT ONLINE, for example in 2:00 AM, or run it manually after closing all PhonerLite copies on PCs in your network

7) Have fun!

If you want to run sync process as a Windows task, just add to each .bat (NOT .vbs) file path to your working directory, for example:
@ECHO OFF
D:
cd D:\mergetest\csv

And create a task to run makephonebook.bat on your server or PC, where client phonebooks are stored, at 02.00 AM (or any time you want) everyday.
Tested and working without any problems.

Creating links in Windows and the need for a special file system (NTFS) is out of scope of PhonerLite. I can't help with this here. Sorry.