open LIST, '>>', '/opt/btb_webservice/ver3/lease_list.txt' or die "/opt/btb_webservice/ver3/lease_list.txt: $!";
print LIST join(' ',$date,$client_ip,$client_mac,$master_ip),"\n" or die "/opt/btb_webservice/ver3/lease_list.txt: $!";
close LIST or die "/opt/btb_webservice/ver3/lease_list.txt: $!";