diff --git a/xwords4/android/XWords4/src/org/eehouse/android/xw4/RelayService.java b/xwords4/android/XWords4/src/org/eehouse/android/xw4/RelayService.java
index 21eaf0353..00d8ce936 100644
--- a/xwords4/android/XWords4/src/org/eehouse/android/xw4/RelayService.java
+++ b/xwords4/android/XWords4/src/org/eehouse/android/xw4/RelayService.java
@@ -531,7 +531,7 @@ public class RelayService extends XWService
                     postData( RelayService.this, token, msg );
                     break;
                 case XWPDEV_ACK:
-                    noteAck( dis.readInt() );
+                    noteAck( vli2un( dis ) );
                     break;
                 default:
                     DbgUtils.logf( "RelayService.gotPacket(): Unhandled cmd" );
@@ -917,7 +917,11 @@ public class RelayService extends XWService
     private static void noteAck( int packetID )
     {
         synchronized( s_packetsSent ) {
-            s_packetsSent.remove( packetID );
+            if ( s_packetsSent.contains( packetID ) ) {
+                s_packetsSent.remove( packetID );
+            } else {
+                DbgUtils.logf( "Weird: got ack %d but never sent", packetID );
+            }
             DbgUtils.logf( "RelayService.noteAck(): Got ack for %d; "
                            + "there are %d unacked packets", 
                            packetID, s_packetsSent.size() );
diff --git a/xwords4/linux/relaycon.c b/xwords4/linux/relaycon.c
index 93c5086c4..33692fcf6 100644
--- a/xwords4/linux/relaycon.c
+++ b/xwords4/linux/relaycon.c
@@ -50,6 +50,7 @@ static int writeHeader( RelayConStorage* storage, XP_U8* dest, XWRelayReg cmd );
 static bool readHeader( const XP_U8** buf, MsgHeader* header );
 static size_t writeDevID( XP_U8* buf, size_t len, const XP_UCHAR* str );
 static size_t writeShort( XP_U8* buf, size_t len, XP_U16 shrt );
+static size_t writeVLI( XP_U8* out, uint32_t nn );
 static size_t un2vli( int nn, uint8_t* buf );
 static bool vli2un( const uint8_t** inp, uint32_t* outp );
 
@@ -185,11 +186,7 @@ sendAckIf( RelayConStorage* storage, const MsgHeader* header )
     if ( header->cmd != XWPDEV_ACK ) {
         XP_U8 tmpbuf[16];
         int indx = writeHeader( storage, tmpbuf, XWPDEV_ACK );
-
-        uint8_t buf[5];
-        size_t numSiz = un2vli( header->packetID, buf );
-        memcpy( &tmpbuf[indx], buf, numSiz );
-        indx += numSiz;
+        indx += writeVLI( &tmpbuf[indx], header->packetID );
         sendIt( storage, tmpbuf, indx );
     }
 }
@@ -251,9 +248,12 @@ relaycon_receive( void* closure, int socket )
                 break;
             }
             case XWPDEV_ACK: {
-                XP_U32 packetID = getNetLong( &ptr );
+                uint32_t packetID;
+                if ( !vli2un( &ptr, &packetID ) ) {
+                    assert( 0 );
+                }
                 XP_USE( packetID );
-                XP_LOGF( "got ack for packetID %ld", packetID );
+                XP_LOGF( "got ack for packetID %d", packetID );
                 break;
             }
             case XWPDEV_ALERT: {
@@ -350,6 +350,15 @@ writeShort( XP_U8* buf, size_t len, XP_U16 shrt )
     return sizeof(shrt);
 }
 
+static size_t
+writeVLI( XP_U8* out, uint32_t nn )
+{
+    uint8_t buf[5];
+    size_t numSiz = un2vli( nn, buf );
+    memcpy( out, buf, numSiz );
+    return numSiz;
+}
+
 static XP_U16
 getNetShort( const XP_U8** ptr )
 {
@@ -387,10 +396,9 @@ writeHeader( RelayConStorage* storage, XP_U8* dest, XWRelayReg cmd )
     }
 
     if ( XWPDEV_PROTO_VERSION_1 == storage->proto ) {
-        uint8_t buf[5];
-        size_t numSiz = un2vli( packetNum, buf );
-        memcpy( &dest[indx], buf, numSiz );
-        indx += numSiz;
+        indx += writeVLI( &dest[indx], packetNum );
+    } else {
+        assert( 0 );
     }
 
     dest[indx++] = cmd;
diff --git a/xwords4/relay/xwrelay.cpp b/xwords4/relay/xwrelay.cpp
index 54b6f1048..6a4fcfa96 100644
--- a/xwords4/relay/xwrelay.cpp
+++ b/xwords4/relay/xwrelay.cpp
@@ -330,7 +330,7 @@ vli2un( const unsigned char** bufpp, const unsigned char* end, uint32_t* out )
         }
     }
 
-    bool success = in < end;
+    bool success = in <= end;
     if ( success ) {
         *bufpp = in;
         *out = result;
@@ -1549,11 +1549,11 @@ static void
 ackPacketIf( const UDPHeader* header, const AddrInfo* addr )
 {
     if ( UDPAckTrack::shouldAck( header->cmd ) ) {
-        uint32_t packetID = header->packetID;
-        logf( XW_LOGINFO, "%s: acking packet %d", __func__, packetID );
-        packetID = htonl( packetID );
-        send_via_udp( addr, NULL, XWPDEV_ACK, 
-                      &packetID, sizeof(packetID), NULL );
+        logf( XW_LOGINFO, "%s: acking packet %d", __func__, header->packetID );
+
+        uint8_t buf[5];
+        size_t siz = un2vli( header->packetID, buf );
+        send_via_udp( addr, NULL, XWPDEV_ACK, buf, siz, NULL );
     }
 }