Finally... my problem have resolved. thanks Conrad and nikkil !! It seems that PC-2 should install Host and have to restart to get steady-going.. if I just run Agent on PC-2(restart still not ok), I will see PC-2 usually changed status from on line and off line on PC-1 GMS windows. even when on connect between PC-2 and PC-3, it only get black screen and can't do any remote control.
1. I have installed GMS on PC-1 use port 25 2. I run Agent on PC-2, set the Internet ID through PC-1, (PC-2 is under firewall block almostly all other private port) I can see the PC-2 connections in PC-A GMS Administration 3. I run viewer on PC-3 (other Internet PC)and add PC-2 that set the Internet ID through PC-1 then, I Logon to PC-2, It seems have successful connection and popup to ask password, I enter the right password and popup a window but only got black screen and can not do any remote control??? :o 4. the strange is when I use microsoft remote desktop to login to PC-2 uner PC-2's local network, at this time, PC-3 can control the PC-2 and not black screen any more?? I diconnect the microsoft remote desktop, then PC-3 become black screen again , why ?