diff --git a/javalib/api/system-current.txt b/javalib/api/system-current.txt
index 04283c2..0fb83ac 100644
--- a/javalib/api/system-current.txt
+++ b/javalib/api/system-current.txt
@@ -4,8 +4,8 @@
   public class VirtualMachine implements java.lang.AutoCloseable {
     method public void clearCallback();
     method public void close();
-    method @NonNull public android.os.IBinder connectToVsockServer(int) throws android.system.virtualmachine.VirtualMachineException;
-    method @NonNull public android.os.ParcelFileDescriptor connectVsock(int) throws android.system.virtualmachine.VirtualMachineException;
+    method @NonNull public android.os.IBinder connectToVsockServer(@IntRange(from=android.system.virtualmachine.VirtualMachine.MIN_VSOCK_PORT, to=android.system.virtualmachine.VirtualMachine.MAX_VSOCK_PORT) long) throws android.system.virtualmachine.VirtualMachineException;
+    method @NonNull public android.os.ParcelFileDescriptor connectVsock(@IntRange(from=android.system.virtualmachine.VirtualMachine.MIN_VSOCK_PORT, to=android.system.virtualmachine.VirtualMachine.MAX_VSOCK_PORT) long) throws android.system.virtualmachine.VirtualMachineException;
     method @NonNull public android.system.virtualmachine.VirtualMachineConfig getConfig();
     method @NonNull public java.io.InputStream getConsoleOutput() throws android.system.virtualmachine.VirtualMachineException;
     method @NonNull public java.io.InputStream getLogOutput() throws android.system.virtualmachine.VirtualMachineException;
@@ -17,6 +17,8 @@
     method public void stop() throws android.system.virtualmachine.VirtualMachineException;
     method @NonNull public android.system.virtualmachine.VirtualMachineDescriptor toDescriptor() throws android.system.virtualmachine.VirtualMachineException;
     field public static final String MANAGE_VIRTUAL_MACHINE_PERMISSION = "android.permission.MANAGE_VIRTUAL_MACHINE";
+    field public static final long MAX_VSOCK_PORT = 4294967295L; // 0xffffffffL
+    field public static final long MIN_VSOCK_PORT = 1024L; // 0x400L
     field public static final int STATUS_DELETED = 2; // 0x2
     field public static final int STATUS_RUNNING = 1; // 0x1
     field public static final int STATUS_STOPPED = 0; // 0x0
diff --git a/javalib/src/android/system/virtualmachine/VirtualMachine.java b/javalib/src/android/system/virtualmachine/VirtualMachine.java
index 1cf808a..87f9f6a 100644
--- a/javalib/src/android/system/virtualmachine/VirtualMachine.java
+++ b/javalib/src/android/system/virtualmachine/VirtualMachine.java
@@ -45,9 +45,11 @@
 
 import android.annotation.CallbackExecutor;
 import android.annotation.IntDef;
+import android.annotation.IntRange;
 import android.annotation.NonNull;
 import android.annotation.Nullable;
 import android.annotation.RequiresPermission;
+import android.annotation.SuppressLint;
 import android.annotation.SystemApi;
 import android.annotation.TestApi;
 import android.content.ComponentCallbacks2;
@@ -121,6 +123,24 @@
             "android.permission.USE_CUSTOM_VIRTUAL_MACHINE";
 
     /**
+     * The lowest port number that can be used to communicate with the virtual machine payload.
+     *
+     * @see #connectToVsockServer
+     * @see #connectVsock
+     */
+    @SuppressLint("MinMaxConstant") // Won't change: see man 7 vsock.
+    public static final long MIN_VSOCK_PORT = 1024;
+
+    /**
+     * The highest port number that can be used to communicate with the virtual machine payload.
+     *
+     * @see #connectToVsockServer
+     * @see #connectVsock
+     */
+    @SuppressLint("MinMaxConstant") // Won't change: see man 7 vsock.
+    public static final long MAX_VSOCK_PORT = (1L << 32) - 1;
+
+    /**
      * Status of a virtual machine
      *
      * @hide
@@ -998,9 +1018,13 @@
      */
     @SystemApi
     @NonNull
-    public IBinder connectToVsockServer(int port) throws VirtualMachineException {
+    public IBinder connectToVsockServer(
+            @IntRange(from = MIN_VSOCK_PORT, to = MAX_VSOCK_PORT) long port)
+            throws VirtualMachineException {
+
         synchronized (mLock) {
-            IBinder iBinder = nativeConnectToVsockServer(getRunningVm().asBinder(), port);
+            IBinder iBinder =
+                    nativeConnectToVsockServer(getRunningVm().asBinder(), validatePort(port));
             if (iBinder == null) {
                 throw new VirtualMachineException("Failed to connect to vsock server");
             }
@@ -1016,10 +1040,12 @@
      */
     @SystemApi
     @NonNull
-    public ParcelFileDescriptor connectVsock(int port) throws VirtualMachineException {
+    public ParcelFileDescriptor connectVsock(
+            @IntRange(from = MIN_VSOCK_PORT, to = MAX_VSOCK_PORT) long port)
+            throws VirtualMachineException {
         synchronized (mLock) {
             try {
-                return getRunningVm().connectVsock(port);
+                return getRunningVm().connectVsock(validatePort(port));
             } catch (RemoteException e) {
                 throw e.rethrowAsRuntimeException();
             } catch (ServiceSpecificException e) {
@@ -1028,6 +1054,16 @@
         }
     }
 
+    private int validatePort(long port) {
+        // Ports below 1024 are "privileged" (payload code can't bind to these), and port numbers
+        // are 32-bit unsigned numbers at the OS level, even though we pass them as 32-bit signed
+        // numbers internally.
+        if (port < MIN_VSOCK_PORT || port > MAX_VSOCK_PORT) {
+            throw new IllegalArgumentException("Bad port " + port);
+        }
+        return (int) port;
+    }
+
     /**
      * Returns the root directory where all files related to this {@link VirtualMachine} (e.g.
      * {@code instance.img}, {@code apk.idsig}, etc) are stored.
diff --git a/tests/aidl/com/android/microdroid/testservice/ITestService.aidl b/tests/aidl/com/android/microdroid/testservice/ITestService.aidl
index 077c74f..a4ecc45 100644
--- a/tests/aidl/com/android/microdroid/testservice/ITestService.aidl
+++ b/tests/aidl/com/android/microdroid/testservice/ITestService.aidl
@@ -17,9 +17,9 @@
 
 /** {@hide} */
 interface ITestService {
-    const int SERVICE_PORT = 5678;
+    const long SERVICE_PORT = 5678;
 
-    const int ECHO_REVERSE_PORT = 6789;
+    const long ECHO_REVERSE_PORT = 0x80000001L; // Deliberately chosen to be > 2^31, < 2^32
 
     /* add two integers. */
     int addInteger(int a, int b);
diff --git a/tests/testapk/src/native/testbinary.cpp b/tests/testapk/src/native/testbinary.cpp
index 8a0019d..b6a7aa2 100644
--- a/tests/testapk/src/native/testbinary.cpp
+++ b/tests/testapk/src/native/testbinary.cpp
@@ -112,7 +112,7 @@
     }
     struct sockaddr_vm server_sa = (struct sockaddr_vm){
             .svm_family = AF_VSOCK,
-            .svm_port = BnTestService::ECHO_REVERSE_PORT,
+            .svm_port = static_cast<uint32_t>(BnTestService::ECHO_REVERSE_PORT),
             .svm_cid = VMADDR_CID_ANY,
     };
     int ret = TEMP_FAILURE_RETRY(bind(server_fd, (struct sockaddr*)&server_sa, sizeof(server_sa)));
diff --git a/virtualizationservice/src/aidl.rs b/virtualizationservice/src/aidl.rs
index 072afec..186052d 100644
--- a/virtualizationservice/src/aidl.rs
+++ b/virtualizationservice/src/aidl.rs
@@ -973,13 +973,16 @@
         if !matches!(&*self.instance.vm_state.lock().unwrap(), VmState::Running { .. }) {
             return Err(Status::new_service_specific_error_str(-1, Some("VM is not running")));
         }
-        let stream =
-            VsockStream::connect_with_cid_port(self.instance.cid, port as u32).map_err(|e| {
-                Status::new_service_specific_error_str(
-                    -1,
-                    Some(format!("Failed to connect: {:?}", e)),
-                )
-            })?;
+        let port = port as u32;
+        if port < 1024 {
+            return Err(Status::new_service_specific_error_str(
+                -1,
+                Some(format!("Can't connect to privileged port {port}")),
+            ));
+        }
+        let stream = VsockStream::connect_with_cid_port(self.instance.cid, port).map_err(|e| {
+            Status::new_service_specific_error_str(-1, Some(format!("Failed to connect: {:?}", e)))
+        })?;
         Ok(vsock_stream_to_pfd(stream))
     }
 }