void handleUploadTerrain (IClientAPI remote_client, string clientFileName)
 {
     if (TerrainUploader == null)
     {
         remote_client.SendAlertMessage ("Uploading terrain file...");
         TerrainUploader = new EstateTerrainXferHandler (remote_client, clientFileName);
         lock (TerrainUploader)
         {
             remote_client.OnXferReceive += TerrainUploader.XferReceive;
             remote_client.OnAbortXfer += AbortTerrainXferHandler;
             TerrainUploader.TerrainUploadDone += HandleTerrainApplication;
         }
         TerrainUploader.RequestStartXfer (remote_client);
     } else
     {
         remote_client.SendAlertMessage ("Another Terrain Upload is in progress.  Please wait your turn!");
     }
 }