diff -r ab577db125c4 -r 36d7e4b6ca81 hedgewars/uLand.pas
--- a/hedgewars/uLand.pas	Sun Nov 21 09:37:48 2010 -0500
+++ b/hedgewars/uLand.pas	Sun Nov 21 17:48:58 2010 +0300
@@ -35,7 +35,7 @@
 
 implementation
 uses uConsole, uStore, uRandom, uLandObjects, uIO, uLandTexture, sysutils,
-     uVariables, uUtils;
+     uVariables, uUtils, uCommands, Adler32;
 
 operator=(const a, b: direction) c: Boolean;
 begin
@@ -1294,8 +1294,35 @@
     GenPreview:= Preview
 end;
 
+
+procedure chLandCheck(var s: shortstring);
+begin
+{$IFDEF DEBUGFILE}
+    AddFileLog('CheckLandDigest: ' + s + ' digest : ' + digest);
+{$ENDIF}
+    if digest = '' then
+        digest:= s
+    else
+        TryDo(s = digest, 'Different maps generated, sorry', true);
+end;
+
+procedure chSendLandDigest(var s: shortstring);
+var adler, i: LongInt;
+begin
+    adler:= 1;
+    for i:= 0 to LAND_HEIGHT-1 do
+        Adler32Update(adler, @Land[i,0], LAND_WIDTH);
+    s:= 'M' + IntToStr(adler);
+
+    chLandCheck(s);
+    SendIPCRaw(@s[0], Length(s) + 1)
+end;
+
 procedure initModule;
 begin
+    RegisterVariable('landcheck', vtCommand, @chLandCheck, false);
+    RegisterVariable('sendlanddigest', vtCommand, @chSendLandDigest, false);
+
     LandBackSurface:= nil;
     digest:= '';