Provide an API to force access to the host

core/src/main/java/org/testcontainers/containers/GenericContainer.java

@@ -231,6 +231,7 @@ public class GenericContainer<SELF extends GenericContainer<SELF>>
     @Setter(AccessLevel.NONE)
     private boolean shouldBeReused = false;
 
+    private boolean hostAccessible = false;
 
     public GenericContainer(@NonNull final DockerImageName dockerImageName) {
         this.image = new RemoteDockerImage(dockerImageName);
@@ -834,6 +835,9 @@ private void applyConfiguration(CreateContainerCmd createCommand) {
             createCommand.withNetworkMode(networkForLinks.get());
         }
 
+        if (hostAccessible) {
+            PortForwardingContainer.INSTANCE.start();
+        }
         PortForwardingContainer.INSTANCE.getNetwork().ifPresent(it -> {
             withExtraHost(INTERNAL_HOST_HOSTNAME, it.getIpAddress());
         });
@@ -1424,6 +1428,18 @@ public SELF withReuse(boolean reusable) {
         return self();
     }
 
+    /**
+     * Forces access to the tests host machine.
+     * Use this method if you need to call {@link org.testcontainers.Testcontainers#exposeHostPorts(int...)}
+     * after you start this container.
+     *
+     * @return this
+     */
+    public SELF withAccessToHost(boolean value) {
+        this.hostAccessible = value;
+        return self();
+    }
+
     @Override
     public boolean equals(Object o) {
         return this == o;

core/src/main/java/org/testcontainers/containers/PortForwardingContainer.java

@@ -15,6 +15,7 @@
 import java.util.Set;
 import java.util.UUID;
 import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.atomic.AtomicReference;
 
 public enum PortForwardingContainer {
     INSTANCE;
@@ -68,9 +69,24 @@ public void exposeHostPort(int hostPort, int containerPort) {
         }
     }
 
+    void start() {
+        getSshConnection();
+    }
+
     Optional<ContainerNetwork> getNetwork() {
         return Optional.ofNullable(container)
             .map(GenericContainer::getContainerInfo)
             .flatMap(it -> it.getNetworkSettings().getNetworks().values().stream().findFirst());
     }
+
+    void reset() {
+        if (container != null) {
+            container.stop();
+        }
+        container = null;
+
+        ((AtomicReference<?>) (Object) sshConnection).set(null);
+
+        exposedPorts.clear();
+    }
 }

core/src/test/java/org/testcontainers/containers/ExposedHostTest.java

@@ -3,6 +3,7 @@
 import com.google.common.collect.ImmutableMap;
 import com.sun.net.httpserver.HttpServer;
 import lombok.SneakyThrows;
+import org.junit.After;
 import org.junit.AfterClass;
 import org.junit.BeforeClass;
 import org.junit.Test;
@@ -31,42 +32,52 @@ public static void setUpClass() throws Exception {
         });
 
         server.start();
-        Testcontainers.exposeHostPorts(server.getAddress().getPort());
-
-        Testcontainers.exposeHostPorts(ImmutableMap.of(server.getAddress().getPort(), 80));
-        Testcontainers.exposeHostPorts(ImmutableMap.of(server.getAddress().getPort(), 81));
     }
 
     @AfterClass
-    public static void tearDownClass() throws Exception {
+    public static void tearDownClass() {
         server.stop(0);
     }
 
+    @After
+    public void tearDown() {
+        PortForwardingContainer.INSTANCE.reset();
+    }
+
+    @Test
+    public void testExposedHostAfterContainerIsStarted() {
+        try (
+            GenericContainer<?> container = new GenericContainer<>(TINY_IMAGE)
+                .withCommand("top")
+                .withAccessToHost(true)
+        ) {
+            container.start();
+            Testcontainers.exposeHostPorts(server.getAddress().getPort());
+            assertResponse(container, server.getAddress().getPort());
+        }
+    }
+
     @Test
     public void testExposedHost() throws Exception {
-        assertResponse(new GenericContainer<>(TINY_IMAGE)
-            .withCommand("top"),
-            server.getAddress().getPort());
+        Testcontainers.exposeHostPorts(server.getAddress().getPort());
+        assertResponse(new GenericContainer<>(TINY_IMAGE).withCommand("top"), server.getAddress().getPort());
     }
 
     @Test
     public void testExposedHostWithNetwork() throws Exception {
+        Testcontainers.exposeHostPorts(server.getAddress().getPort());
         try (Network network = Network.newNetwork()) {
-            assertResponse(new GenericContainer<>(TINY_IMAGE)
-                .withNetwork(network)
-                .withCommand("top"),
-                server.getAddress().getPort());
+            assertResponse(new GenericContainer<>(TINY_IMAGE).withNetwork(network).withCommand("top"), server.getAddress().getPort());
         }
     }
 
     @Test
     public void testExposedHostPortOnFixedInternalPorts() throws Exception {
-        assertResponse(new GenericContainer<>(TINY_IMAGE)
-            .withCommand("top"),
-            80);
-        assertResponse(new GenericContainer<>(TINY_IMAGE)
-            .withCommand("top"),
-            81);
+        Testcontainers.exposeHostPorts(ImmutableMap.of(server.getAddress().getPort(), 80));
+        Testcontainers.exposeHostPorts(ImmutableMap.of(server.getAddress().getPort(), 81));
+
+        assertResponse(new GenericContainer<>(TINY_IMAGE).withCommand("top"), 80);
+        assertResponse(new GenericContainer<>(TINY_IMAGE).withCommand("top"), 81);
     }
 
     @SneakyThrows