why this listenSocket code in a thread function

[Scott]

pthread_create(&threadDns, NULL, ThreadDNS, dnsThread[i])
may run many times?

bitcoin-seeder/dns.c

Lines 390 to 410 in d54f39a

 if (listenSocket == -1) { 
   struct sockaddr_in6 si_me; 
   if ((listenSocket=socket(AF_INET6, SOCK_DGRAM, IPPROTO_UDP))==-1) { 
     listenSocket = -1; 
     return -1; 
   } 
   replySocket = socket(AF_INET6, SOCK_DGRAM, IPPROTO_UDP); 
   if (replySocket == -1) 
   { 
     close(listenSocket); 
     return -1; 
   } 
   int sockopt = 1; 
   setsockopt(listenSocket, IPPROTO_IPV6, DSTADDR_SOCKOPT, &sockopt, sizeof sockopt); 
   memset((char *) &si_me, 0, sizeof(si_me)); 
   si_me.sin6_family = AF_INET6; 
   si_me.sin6_port = htons(opt->port); 
   si_me.sin6_addr = in6addr_any; 
   if (bind(listenSocket, (struct sockaddr*)&si_me, sizeof(si_me))==-1) 
     return -2; 
 } 

[Scott]

ok, these is a sleep in createthread loop.
: )