Arduino WiFi Shield UDP Support

Hi everyone!!!
I have a bit problem with example WiFiUdpSendRecieveSting
First time I debug, it works very well. (I send 3 string "acb")

Port open
Attempting to connect to SSID: Connectify-Minh
Connected to wifi
SSID: Connectify-Minh
IP Address: 192.168.12.101
signal strength (RSSI):-49 dBm

Starting connection to server...
Received packet of size 3
From 192.168.12.1, port 2390
Contents:
acb
Received packet of size 3
From 192.168.12.1, port 2390
Contents:
acb
Received packet of size 3
From 192.168.12.1, port 2390
Contents:
acb

Second time I debug, it just recieved once and didn't send "acknowledged".... (I send 3 string "acb")

Port open
Attempting to connect to SSID: Connectify-Minh
Connected to wifi
SSID: Connectify-Minh
IP Address: 192.168.12.101
signal strength (RSSI):-49 dBm

Starting connection to server...
Received packet of size 3
From 0.0.0.0, port 0
Contents:
123

Third time, it doesn't run anymore.

Port open

Plz show me my misstake!!! Thank for your help :smiley: