inbound TCP and serviceActivator response gets stuck

[hatim]

I have configured inbound TCP service which is more or less like how it is described for UDP in http://blog.springsource.com/2010/03...ration-2-0-m3/

I can execute

echo -e "Hello\r\n" | nc localhost 9901 

easily for void accumultae, but not for some thing which returns a value

I am getting the folliwng trace

DirectChannel: preSend on channel 'tcpChannel', message: [Payload=[B@578baf24][Headers={$ip_hostname=127.0.0.1, $ip_address=127.0.0.1, $timestamp=1270747841142, $history=[{timestamp=1270747841144, componentName=tcpChannel, componentType=channel}], $id=90499407-bb6c-4085-9308-7c9069b6e829}]
ServiceActivatingHandler: ServiceActivator for [com.tesenso.trackandroute.biz.Persister]] received message: [Payload=[B@578baf24][Headers={$ip_hostname=127.0.0.1, $ip_address=127.0.0.1, $timestamp=1270747841142, $history=[{timestamp=1270747841144, componentName=tcpChannel, componentType=channel}, {timestamp=1270747841145, componentName=activator, componentType=service-activator}], $id=90499407-bb6c-4085-9308-7c9069b6e829}]
5
ServiceActivatingHandler: handler 'ServiceActivator for [com.tesenso.trackandroute.biz.Persister]]' sending reply Message: [Payload=1
][Headers={$ip_hostname=127.0.0.1, $ip_address=127.0.0.1, $timestamp=1270747841142, $history=[{timestamp=1270747841144, componentName=tcpChannel, componentType=channel}, {timestamp=1270747841145, componentName=activator, componentType=service-activator}], $id=90499407-bb6c-4085-9308-7c9069b6e829}]
DirectChannel: preSend on channel 'tcpChannel', message: [Payload=1
][Headers={$ip_hostname=127.0.0.1, $ip_address=127.0.0.1, $timestamp=1270747841142, $history=[{timestamp=1270747841144, componentName=tcpChannel, componentType=channel}, {timestamp=1270747841145, componentName=activator, componentType=service-activator}, {timestamp=1270747841209, componentName=tcpChannel, componentType=channel}], $id=90499407-bb6c-4085-9308-7c9069b6e829}]
ServiceActivatingHandler: ServiceActivator for [com.tesenso.trackandroute.biz.Persister]] received message: [Payload=1
][Headers={$ip_hostname=127.0.0.1, $ip_address=127.0.0.1, $timestamp=1270747841142, $history=[{timestamp=1270747841144, componentName=tcpChannel, componentType=channel}, {timestamp=1270747841145, componentName=activator, componentType=service-activator}, {timestamp=1270747841209, componentName=tcpChannel, componentType=channel}, {timestamp=1270747841209, componentName=activator, componentType=service-activator}], $id=90499407-bb6c-4085-9308-7c9069b6e829}]
GenericConversionService: Conditional converter lookup [DID NOT MATCH] org.springframework.core.convert.support.IdToEntityConverter@31dbfb7a
GenericConversionService: Conditional converter lookup [DID NOT MATCH] org.springframework.core.convert.support.ObjectToObjectConverter@615b2028
GenericConversionService: Conditional converter lookup [DID NOT MATCH] org.springframework.core.convert.support.ObjectToArrayConverter@259c5407 

What I need is to get a message from TCP and reply to it instantly after posting it to a JMS queue. The reply needs to be tailored (ie I need to send Date, Time and some other parameters)

[Gary Russell]

In Spring Integration, Channel Adapters are unidrectional devices (inbound or outbound). You need an inbound TCP Gateway, which we are considering; vote for the JIRA here...

https://jira.springsource.org/browse/INT-1008

[hatim]

I see, for some reason I thought that Gateway only affected once you got more than one message on the same channel and needed some state to maintain to route them back.

But in the case if JIRA issue is far away, could you suggest any modification to current implementation. I just need to send customized responses to incoming TCP requests (which I then offload to JMS for processing). So every response is essentially a success response (assuming things were put in JMS wueue) and response will include some simple text (like current time + OK, or it may include more data like advice on time of next TCP inbound message)

[Gary Russell]

@hatim

The challenge is correlating responses to clients. If you only need to support a single client, one way to quickly do it would be as follows...

Subclass the TcpNetReceivingChannelAdapter. Add an instance variable

private PollableChannel responseChannel;

as well as a setter.

Copy the handleSocketMethod from TcpNetReceivingChannelAdapter into the subclass. I hate copying all that code but it would need a little refactoring to provide an extension point here.

In that method, after sendMessage(message) add the following...

Message<String> out = (Message<String>) responseChannel.receive();
socket.getOutputStream().write(out.getPayload().getBytes());

(Note this will only work if there is one client connected to the Gateway; otherwise you'd need code to look at the the message headers and correlate the response, and the receive would have to be done on another thread and the response messages distributed to the appropriate socket).


The Spring config would look something like...

	<bean id="tcpGateway" class="my.TcpNetReceivingGateway">
		<constructor-arg value="15300"/>
		<property name="outputChannel" ref="toSA"/>
		<property name="responseChannel" ref="fromSA"/>
		<property name="messageFormat" value="#{T(org.springframework.integration.ip.tcp.MessageFormats).FORMAT_CRLF}" />
	</bean>

	<int:channel id="toSA" />
	
	<int:channel id="fromSA">
		<int:queue capacity="1"/>
	</int:channel>
	
	<int:service-activator id="SA" 
		input-channel="toSA"
		output-channel="fromSA"
		ref="sa"
		method="test"
	/>
	
	<bean id="sa" class="my.TestSA" />

TestSA

	public String test(byte[] bytes) {
		System.out.println("Received " + new String(bytes));
		return "OK";
	}

Result

echo -e "abc\r\n" | nc localhost 15300
OK

Note that this is not how the actual gateway will be implemented; it is just a quick and dirty way to get what you need.

HTH

Gary

[Gary Russell]

And, if you *do* need to support multiple clients this way, it should be relatively easy - just have a (synchronized) Map<Object,Socket> instance variable. After the send(), put the socket in the map, with the $id as a key.

Change the responseChannel to a SubscribableChannel; implement MessageHandler and subscribe to it. In handleMessage(), examine the $id in the header and use it as a key to the Map to get the socket, send the response to the socket and remove the entry from the Map.

[hatim]

@Gary
I tried the newly put telnet server as well as this approach.

The telnet server works fine with telnet client. how ever I am not getting any thing with nc echo -e "abc\r\n" | nc localhost 15300

Also when using a service activator, If I specify a output channel, the systems goes hay wire.

The current application I am working with sends in a TCP messages and waits for an OK or Error TCP response and then closes the socket.

[Gary Russell]

@Hatim

Works fine for me (both telnet and nc).

See src/test/java/.../SimpleTcpNetInboundGatewayTests.java.

I just ran this in debug mode after setting a breakpoint on line 152 (this holds the gateways open so we can test them interactively).

Here are my results; note that the port may not be 5200 for you if that port is already in use (the test case finds the first available port starting at 5200).

gpr@arwen:~$ telnet localhost 5200
Trying ::1...
Connected to localhost.
Escape character is '^]'.
abc
echo:abc
^]

telnet> quit
Connection closed.



gpr@arwen:~$ echo -e "abc\r\n" | nc localhost 5200
echo:abc
^C

The service in the test case is a simple echo service.

Please explain what you mean by "goes haywire". You don't need an output channel in this case because the gateway uses a temporary channel to receive the result.

In any case, I added an output channel to this test case without any impact.

Thanks

[hatim]

@Gary

Actually I did find the error and that it was incorrect use of cr+lf in the message being sent (from the sensor I am working with).

sorry for being imprecise, I just needed some food to restart my brain

But the following is working for me,

 <int:channel id="telnetInTransformerChannel" />

        <ip:inbound-gateway id="telnetGateway"
                   pool-size="10"
               port="9901"
               request-channel="telnetInTransformerChannel"
                message-format="crlf" />

   

   <int:service-activator
                id="activator"
                method="accumulate"
                input-channel="telnetInTransformerChannel"
                ref="persister" />

        <bean id="persister" class="blah.service.Persister" /> 

And the method being

@Service
@Transactional
public class Persister {

        @ServiceActivator
        public String accumulate(byte[] buffer) {
                System.out.println(new String(buffer));
                InboundMessage ibm = new InboundMessage();
                ibm.setMessage(new String(buffer));

                //we need to send UTC here
                ibm.setTimeRecieved(new Date());
                ibm.persist();
                SimpleDateFormat f = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        return "OK(" + f.format(new Date()) + ")" ;

        }

}

But I will try to reproduce the infinite loop again later (I think it had to do some thing with return type being bye[] and service activator in the tcpGateway code poasted before, which I think should not be used since we now have a better alternative

Really appreciate your help