Index: common/Message.cpp
===================================================================
--- common/Message.cpp	(revision b650f8ae14a68b3877a3c1aaf68a5475fc22478d)
+++ common/Message.cpp	(revision 787806fd4402d85c3337e6f4b996f989e475a290)
@@ -24,10 +24,10 @@
 }
 
-int receiveMessage(NETWORK_MSG *msg, int sock, struct sockaddr_in *dest)
+int receiveMessage(NETWORK_MSG *msg, int sock, struct sockaddr_in *source)
 {
    socklen_t socklen = sizeof(struct sockaddr_in);
 
    // assume we don't care about the value of socklen
-   int ret =  recvfrom(sock, (char*)msg, sizeof(NETWORK_MSG), 0, (struct sockaddr *)dest, &socklen);
+   int ret =  recvfrom(sock, (char*)msg, sizeof(NETWORK_MSG), 0, (struct sockaddr *)source, &socklen);
 
    return ret;
Index: common/Message.h
===================================================================
--- common/Message.h	(revision b650f8ae14a68b3877a3c1aaf68a5475fc22478d)
+++ common/Message.h	(revision 787806fd4402d85c3337e6f4b996f989e475a290)
@@ -2,19 +2,20 @@
 #define _MESSAGE_H
 
-#define MSG_TYPE_REGISTER          1
-#define MSG_TYPE_LOGIN             2
-#define MSG_TYPE_LOGOUT            3
-#define MSG_TYPE_CHAT              4
-#define MSG_TYPE_PLAYER            5  // server sends this to update player positions
-#define MSG_TYPE_PLAYER_MOVE       6  // client sends this when a player wants to move
-#define MSG_TYPE_OBJECT            7
-#define MSG_TYPE_REMOVE_OBJECT     8
-#define MSG_TYPE_PICKUP_FLAG       9
-#define MSG_TYPE_DROP_FLAG         10
-#define MSG_TYPE_SCORE             11
-#define MSG_TYPE_START_ATTACK      12
-#define MSG_TYPE_ATTACK            13
-#define MSG_TYPE_PROJECTILE        14
-#define MSG_TYPE_REMOVE_PROJECTILE 15
+#define MSG_TYPE_ACK               1
+#define MSG_TYPE_REGISTER          2
+#define MSG_TYPE_LOGIN             3
+#define MSG_TYPE_LOGOUT            4
+#define MSG_TYPE_CHAT              5
+#define MSG_TYPE_PLAYER            6  // server sends this to update player positions
+#define MSG_TYPE_PLAYER_MOVE       7  // client sends this when a player wants to move
+#define MSG_TYPE_OBJECT            8
+#define MSG_TYPE_REMOVE_OBJECT     9
+#define MSG_TYPE_PICKUP_FLAG       10
+#define MSG_TYPE_DROP_FLAG         11
+#define MSG_TYPE_SCORE             12
+#define MSG_TYPE_START_ATTACK      13
+#define MSG_TYPE_ATTACK            14
+#define MSG_TYPE_PROJECTILE        15
+#define MSG_TYPE_REMOVE_PROJECTILE 16
 
 typedef struct
@@ -26,5 +27,5 @@
 int sendMessage(NETWORK_MSG *msg, int sock, struct sockaddr_in *dest);
 
-int receiveMessage(NETWORK_MSG *msg, int sock, struct sockaddr_in *dest);
+int receiveMessage(NETWORK_MSG *msg, int sock, struct sockaddr_in *source);
 
 #endif