func main() {
args := os.Args
if len(args) != 4 {
fmt.Println("Usage: [aserver UDP ip:port] [fserver RPC ip:port] [secret]")
os.Exit(-1)
}
aserverUDPIpPort := args[1]
fserverRCPIpPort := args[2]
secret := parseSecretArg(args[3])
udpListener := clientServerUtils.InitUDPConn(aserverUDPIpPort)
//Initialize hash table of (udpIpPort, nonce) key-value pairs
var nonceMap clientServerUtils.ConcurrentMap
nonceMap.Map = make(map[string]int64)
//Start listen/receive connection loop
for {
var buf [1024]byte
msgLen, clientUDPAddr, err := udpListener.ReadFromUDP(buf[:])
if err != nil {
fmt.Println("Error on ReadFromUDP: ", err)
} else {
go handleUDPConn(udpListener, clientUDPAddr, fserverRCPIpPort, nonceMap, secret, buf[0:msgLen])
}
}
udpListener.Close()
}
//Generate new nonce for udpAddr and add to nonceMap
func generateNewNonce(udpAddr *net.UDPAddr, nonceMap clientServerUtils.ConcurrentMap) int64 {
nonce := rand.Int63()
nonceMap.Lock()
nonceMap.Map[udpAddr.String()] = nonce
nonceMap.Unlock()
return nonce
}
func handleUDPConn(udpListener net.UDPConn, clientUDPAddr *net.UDPAddr, fserverRCPIpPort string, nonceMap clientServerUtils.ConcurrentMap, secret int64, msgFromClient []byte) {
nonceMap.RLock()
clientNonce := nonceMap.Map[clientUDPAddr.String()]
nonceMap.RUnlock()
var receivedHashMsg clientServerUtils.HashMessage
err := json.Unmarshal(msgFromClient, &receivedHashMsg)
if err != nil {
sendNewNonce(udpListener, clientUDPAddr, nonceMap)
} else if clientNonce == 0 {
errMsg := clientServerUtils.ErrMessage{"unknown remote client address"}
sendErrMessage(udpListener, clientUDPAddr, errMsg)
} else if isValidHashMessage(receivedHashMsg, clientNonce, secret) {
replyWithFortuneInfoMessage(udpListener, clientUDPAddr, fserverRCPIpPort)
} else {
errMsg := clientServerUtils.ErrMessage{"unexpected hash value"}
sendErrMessage(udpListener, clientUDPAddr, errMsg)
}
}