Unable to reply to UDP message

I am trying to send a message using

netcat -u localhost 11111abcd

      

        
        
        
      

    

I just need the client to receive a response: OK. He receives the message and tries to reply with OK. But it writes this endlessly to the application log:

Message: GenericMessage [payload = byte [2], headers = {ip_packetAddress = 127.0.0.1/127.0.0.1: 49489, ip_address = 127.0.0.1, id = 8db6aa3b-b56b-6dce-9554-c7b0ce050142, ip_portname = 49489, ip_host_host_host 127.0.0.1, timestamp = 1494442285767}]

Message payload: OK

Config:

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:int="http://www.springframework.org/schema/integration"
    xmlns:int-ip="http://www.springframework.org/schema/integration/ip"
    xmlns:context="http://www.springframework.org/schema/context"
    xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd
        http://www.springframework.org/schema/integration http://www.springframework.org/schema/integration/spring-integration.xsd
        http://www.springframework.org/schema/integration/ip http://www.springframework.org/schema/integration/ip/spring-integration-ip.xsd">

  <int:channel id="sendUdp"/>

  <int-ip:udp-outbound-channel-adapter id="udpOut" host="localhost" port="11111"
                                   multicast="false" check-length="false"
                                   channel="sendUdp" />

  <int-ip:udp-inbound-channel-adapter id="udpIn" port="11111" receive-buffer-size="500"
                                  multicast="false" check-length="false"
                                  channel="receiveUdp"/>

  <int:service-activator id="updHandler" input-channel="receiveUdp" output-channel="sendUdp" ref="listener"/>

</beans>

@ServiceActivator
public String handle(Message<?> message) {
    System.out.println("*** Message: " + message);
    String command = new String((byte[]) message.getPayload());
    System.out.println("*** Message Payload: "
            + command);
    String response = "OK";

    return response;
}