[java.net.SocketException: Connection reset by peer : socket write error]

i have downloaded minecraft tekkit and the server
it workt for about a week
something happend and now the server is not conettible through external ip (internal everything works)
i work in the ict so the port forwart is ok (my laptop has dmz) canyouseeme.org confurms  port is open the error is :
java.net.SocketException: Connection reset by peer : socket write error

the things i have tryed is:
reinstal java 64 and 32 bit
reinstal minecraft
reinstal tekkit
reinstal tekkit server
opening a new tekkit server whit new world
disabled virus scanner
disabled firewall
reinstalled network driver wlan and lan
opening a vmware machine installed windows 7 and a tekkit server
installed old java version
removing mods from the mods folder
adjusting the server.properties file
other minecraft version
resetting my modem
factory settings modem
calling profider (if thay have blocked java or anything else)
change dns server (tip in youtube film)

my laptop specs are
windows 7 home preminum
500gb ssd 50% free
12gb memory 6 allowcated to minecraft tekkit server
(java -Xmx6G -Xms5G -jar TekkitLite.jar nogui)
cpu intel i7
vga nvidia geforce gtx 850m
500mbit up and down
and yes minecraft is legal

any other ideas how to fixthis error
java.net.SocketException: Connection reset by peer : socket write error