* Improve TcpInboundGateway logic to check for connectionFactory is set in the onInit()

* Improve `UnicastSendingMessageHandler.restartAckThread()` to reflect the proper state of the `UnicastSendingMessageHandler`

Author: artembilan

spring-integration-ip/src/main/java/org/springframework/integration/ip/tcp/TcpInboundGateway.java

@@ -203,6 +203,8 @@ public String getComponentType() {
 	@Override
 	protected void onInit() {
 		super.onInit();
+		Assert.state(this.serverConnectionFactory != null || this.clientConnectionFactory != null,
+				"An 'AbstractConnectionFactory' must not be provided.");
 		if (this.isClientMode) {
 			Assert.notNull(this.clientConnectionFactory, "For client-mode, connection factory must be type='client'");
 			Assert.isTrue(!this.clientConnectionFactory.isSingleUse(),

spring-integration-ip/src/main/java/org/springframework/integration/ip/udp/UnicastSendingMessageHandler.java

@@ -282,7 +282,7 @@ protected void doStop() {
 	@Override
 	public void handleMessageInternal(Message<?> message) {
 		if (this.acknowledge) {
-			Assert.state(this.isRunning(), "When 'acknowledge' is enabled, adapter must be running");
+			Assert.state(isRunning(), "When 'acknowledge' is enabled, adapter must be running");
 			startAckThread();
 		}
 		CountDownLatch countdownLatch = null;
@@ -568,9 +568,11 @@ public void run() {
 	 * (bind) error occurred, without bouncing the JVM.
 	 */
 	public void restartAckThread() {
-		if (this.taskExecutor != null) {
-			this.taskExecutor.execute(this);
-		}
+		Assert.state(this.acknowledge,
+				"The UnicastSendingMessageHandler has to be in the 'acknowledgment' mode to run ack thread.");
+		Assert.state(this.taskExecutor != null,
+				"The UnicastSendingMessageHandler is not running to schedule an ack thread.");
+		this.taskExecutor.execute(this);
 	}
 
 	private void closeSocketIfNeeded() {