Scan for port near default

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/web/ServerProperties.java

@@ -113,7 +113,7 @@ public class ServerProperties implements EmbeddedServletContainerCustomizer {
 	public void customize(ConfigurableEmbeddedServletContainerFactory factory) {
 		Integer port = getPort();
 		if (this.scan) {
-			port = SocketUtils.findAvailableTcpPort(port != null ? 8080 : port);
+			port = scanForPort(port);
 		}
 		if (port != null) {
 			factory.setPort(port);
@@ -132,6 +132,26 @@ public class ServerProperties implements EmbeddedServletContainerCustomizer {
 		}
 	}
 
+	private Integer scanForPort(Integer port) {
+		boolean found = false;
+		int delta = 1;
+		port = port == null ? 8080 : port;
+		while (!found) {
+			try {
+				port = SocketUtils.findAvailableTcpPort(port, port + delta);
+				found = true;
+			}
+			catch (IllegalStateException e) {
+				if (delta > 65536) {
+					throw e;
+				}
+				delta = delta > 5 ? delta > 100 ? delta * 4 : delta * 3 : delta * 2;
+			}
+			port = port + delta;
+		}
+		return port;
+	}
+
 	public static class Tomcat {
 
 		private String accessLogPattern;

spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/web/ServerPropertiesTests.java

@@ -80,6 +80,15 @@ public class ServerPropertiesTests {
 		assertTrue(factory.getPort() > 1000);
 	}
 
+	@Test
+	public void testPortScanFromHigher() throws Exception {
+		this.properties.setScan(true);
+		this.properties.setPort(5678);
+		ConfigurableEmbeddedServletContainerFactory factory = new MockEmbeddedServletContainerFactory();
+		this.properties.customize(factory);
+		assertTrue(factory.getPort() < 6000);
+	}
+
 	// FIXME test customize
 
 }