public void init() throws Exception {
phyLayer = new PhyLayer(this);
database = new Database();
appRcv = new AppRcv(this);
appSnd = new AppSnd(this);
transpLayer = new TransportLayer(this);
lnkRcv = new LnkRcv(this);
lnkSnd = new LnkSnd(this);
appRcv.setAppSnd(appSnd);