How to config tcp server to receive data from multiple client using spring boot? - spring-integration

Question

I would like to configure TCP server to receive and reply data from multiple clients. I searched many other thread but could not found exact way to do. I'm using spring integration first time and have no experience.
Server requirement
should be able to receive and reply data to specific client (can have multiple client, each client should processed separately)
should be able to send data to client and wait for response for specific timeout.
Should be able to detect client is disconnect or not. if Client is disconnect then connection should be closed to save memory. (In earlier method without spring integration I was able to do it by ping client and see sending is failed or not but don't know how to do with spring integration)
I tried below code, In which I'm able to send data to client but could achieve my above requirements
TCP Server Configuration:
#Configuration
public class TcpServerConfig {
private List<TcpConnectionOpenEvent> clientList = new ArrayList<>();
public List<TcpConnectionOpenEvent> getClientList() {
return clientList;
}
#Bean
public TcpReceivingChannelAdapter server(TcpNetServerConnectionFactory cf) {
TcpReceivingChannelAdapter adapter = new TcpReceivingChannelAdapter();
adapter.setConnectionFactory(cf);
adapter.setOutputChannel(inputChannel());
return adapter;
}
#Bean
public MessageChannel inputChannel() {
return new QueueChannel();
}
#Bean
public MessageChannel outputChannel() {
return new DirectChannel();
}
#Bean
public TcpNetServerConnectionFactory cf() {
return new TcpNetServerConnectionFactory(1001);
}
#Bean
public IntegrationFlow outbound() {
return IntegrationFlows.from(outputChannel())
.handle(sender())
.get();
}
#Bean
public MessageHandler sender() {
TcpSendingMessageHandler tcpSendingMessageHandler = new TcpSendingMessageHandler();
tcpSendingMessageHandler.setConnectionFactory(cf());
return tcpSendingMessageHandler;
}
#Bean
public ApplicationListener<TcpConnectionOpenEvent> listener() {
return new ApplicationListener<TcpConnectionOpenEvent>() {
#Override
public void onApplicationEvent(TcpConnectionOpenEvent event) {
outputChannel().send(MessageBuilder.withPayload("foo")
.setHeader(IpHeaders.CONNECTION_ID, event.getConnectionId())
.build());
clientList.add(event);
}
};
}
}
Test Code:
#Service
public class Test {
private static final Logger LOGGER = LoggerFactory.getLogger(MessageServiceImpl.class);
#Autowired
TcpServerConfig tcpServerConfig;
#Autowired
private MessageChannel outputChannel;
#Autowired
private MessageChannel inputChannel;
#Scheduled(fixedRate = 1000)
void task() {
LOGGER.info("Client count: " + tcpServerConfig.getClientList().size());
for (TcpConnectionOpenEvent client : tcpServerConfig.getClientList()) {
outputChannel.send(MessageBuilder.withPayload("foo")
.setHeader(IpHeaders.CONNECTION_ID, client.getConnectionId())
.build());
}
}
}
Any help would be appreciated.

Answer 1

Here is one solution:
#SpringBootApplication
#EnableScheduling
public class So62877512ServerApplication {
public static void main(String[] args) {
SpringApplication.run(So62877512ServerApplication.class, args);
}
#Bean
public IntegrationFlow serverIn(Handler handler) {
return IntegrationFlows.from(Tcp.inboundAdapter(server()))
.transform(Transformers.objectToString())
.filter(handler, "existingConnection", spec -> spec
.discardFlow(f -> f
.handle(handler, "sendInitialReply")))
.handle(handler, "reply")
.get();
}
#Bean
public IntegrationFlow serverOut() {
return f -> f.handle(Tcp.outboundAdapter(server()));
}
#Bean
public TcpServerConnectionFactorySpec server() {
return Tcp.netServer(1234)
.serializer(TcpCodecs.lf())
.deserializer(TcpCodecs.lf()); // compatible with netcat
}
}
#Component
#DependsOn("serverOut")
class Handler {
private static final Logger LOG = LoggerFactory.getLogger(Handler.class);
private final ConcurrentMap<String, BlockingQueue<Message<?>>> clients = new ConcurrentHashMap<>();
private final MessageChannel out;
private final TcpNetServerConnectionFactory server;
public Handler(#Qualifier("serverOut.input") MessageChannel out, TcpNetServerConnectionFactory server) {
this.out = out;
this.server = server;
}
public boolean existingConnection(Message<?> message) {
String connectionId = message.getHeaders().get(IpHeaders.CONNECTION_ID, String.class);
boolean containsKey = this.clients.containsKey(connectionId);
if (!containsKey) {
this.clients.put(connectionId, new LinkedBlockingQueue<Message<?>>());
}
return containsKey;
}
public void sendInitialReply(Message<String> message) {
LOG.info("Replying to " + message.getPayload());
this.out.send(MessageBuilder.withPayload(message.getPayload().toUpperCase())
.copyHeaders(message.getHeaders()).build());
}
#Scheduled(fixedDelay = 5000)
public void sender() {
this.clients.forEach((key, queue) -> {
try {
this.out.send(MessageBuilder.withPayload("foo")
.setHeader(IpHeaders.CONNECTION_ID, key).build());
Message<?> reply = queue.poll(10, TimeUnit.SECONDS);
if (reply == null) {
LOG.error("Timeout waiting for " + key);
this.server.closeConnection(key);
}
else {
LOG.info("Reply " + reply.getPayload() + " from " + key);
}
}
catch (InterruptedException e) {
Thread.currentThread().interrupt();
LOG.error("Interrupted");
}
catch (Exception e) {
LOG.error("Failed to send to " + key, e);
}
});
}
public void reply(Message<String> in) {
BlockingQueue<Message<?>> queue = this.clients.get(in.getHeaders().get(IpHeaders.CONNECTION_ID, String.class));
if (queue != null) {
queue.add(in);
}
}
#EventListener
public void closed(TcpConnectionCloseEvent event) {
this.clients.remove(event.getConnectionId());
LOG.info(event.getConnectionId() + " closed");
}
}
$ nc localhost 1234
foo <- typed
FOO
foo
bar <- typed
foo
bar <- typed
foo
$ <- closed by server - timeout
2020-07-14 14:41:04.906 INFO 64763 --- [pool-1-thread-2] com.example.demo.Handler : Replying to foo
2020-07-14 14:41:13.841 INFO 64763 --- [ scheduling-1] com.example.demo.Handler : Reply bar from localhost:65115:1234:a9fc7e3d-4dda-4627-b765-4f0bb0835153
2020-07-14 14:41:21.465 INFO 64763 --- [ scheduling-1] com.example.demo.Handler : Reply bar from localhost:65115:1234:a9fc7e3d-4dda-4627-b765-4f0bb0835153
2020-07-14 14:41:36.473 ERROR 64763 --- [ scheduling-1] com.example.demo.Handler : Timeout waiting for localhost:65115:1234:a9fc7e3d-4dda-4627-b765-4f0bb0835153
2020-07-14 14:41:36.474 INFO 64763 --- [ scheduling-1] com.example.demo.Handler : localhost:65115:1234:a9fc7e3d-4dda-4627-b765-4f0bb0835153 closed