Added BitmessageContext method to resent unacknowledged messages and updated README.md

core/src/main/java/ch/dissem/bitmessage/BitmessageContext.java

@@ -221,10 +221,33 @@ public class BitmessageContext {
         return ctx.getNetworkHandler().send(server, port, request);
     }
 
+    /**
+     * Removes expired objects from the inventory. You should call this method regularly,
+     * e.g. daily and on each shutdown.
+     */
     public void cleanup() {
         ctx.getInventory().cleanup();
     }
 
+    /**
+     * Sends messages again whose time to live expired without being acknowledged. (And whose
+     * recipient is expected to send acknowledgements.
+     * <p>
+     *     You should call this method regularly, but be aware of the following:
+     *     <ul>
+     *         <li>As messages might be sent, POW will be done. It is therefore not advised to
+     *         call it on shutdown.</li>
+     *         <li>It shouldn't be called right after startup, as it's possible the missing
+     *         acknowledgement was sent while the client was offline.</li>
+     *         <li>Other than that, the call isn't expensive as long as there is no message
+     *         to send, so it might be a good idea to just call it every few minutes.</li>
+     *     </ul>
+     * </p>
+     */
+    public void resendUnacknowledgedMessages() {
+        ctx.resendUnacknowledged();
+    }
+
     public boolean isRunning() {
         return ctx.getNetworkHandler().isRunning();
     }

core/src/test/java/ch/dissem/bitmessage/BitmessageContextTest.java

@@ -309,7 +309,7 @@ public class BitmessageContextTest {
         assertTrue(plaintext.getTo().has(Pubkey.Feature.DOES_ACK));
         when(ctx.messages().findMessagesToResend()).thenReturn(Collections.singletonList(plaintext));
         when(ctx.messages().getMessage(any(byte[].class))).thenReturn(plaintext);
-        ctx.internals().resendUnacknowledged();
+        ctx.resendUnacknowledgedMessages();
         verify(ctx.labeler(), timeout(1000).times(1)).markAsSent(eq(plaintext));
     }
 }