In　this　paper,　we　propose　a　new　UDP-based　and　rate-based　application　layer　protocol,　named　UAP.　The　main　objective　of　UAP　is　to　meet　the　needs　of　the　applications　to　have　all　the　following　merits:　reliability,　real　time,　fairness,　file-transport,　P2P-friendliness　and　TCP-friendliness.　However,　the　previous　studies　of　UDP-based　application　layer　protocol　have　only　focuses　on　certain　parts　of　the　above　characteristics,　such　as　reliability　and　file-transport,　not　all　of　them　as　UAP　did.　Moreover,　in　order　to　be　used　easily,　UAP　is　designed　to　be　connectionless;　as　a　result,　the　interface　is　very　succinct.　Our　experimental　results　justify　that　UAP　is　a　promising　protocol　for　certain　applications.　©　2011　IEEE.