On a suggestion from Domagoj, make the receive window much larger,

providing about a 5x improvement in receive performance on my phone.

doc/index.html

@@ -224,7 +224,7 @@ regular <tt>rsa</tt> key for greatest compatibility.
 <h2>Change Log</h2>
 
 <ul>
-<li> <b>2019/09/XXX Version 24:</b> Fix crash with "Start on Open" on Android 9. New TV icon.  Slightly faster.
+<li> <b>2019/09/XXX Version 24:</b> Fix crash with "Start on Open" on Android 9. New TV icon.  Improve performance.
 <li> <b>2019/09/21 Version 23:</b> Support Android TV.
 <li> <b>2019/09/01 Version 22:</b> Add broadcast intents for start and stop.
 <li> <b>2019/08/11 Version 21:</b> Fix restarting after a crash.  Fix SIGSEGV on some Android 9 devices.

jni/config.h

@@ -34,6 +34,9 @@
 
 #define LOCALOPTIONS_H_EXISTS 1
 
+/* this makes dropbear much faster at receiving files */
+#define DEFAULT_RECV_WINDOW 524288
+#define RECV_MAX_PAYLOAD_LEN (524288+16384)
 
 /* in jni/interface.c: */
 extern const char *conf_path;