Improve async/background handling.
Improve async/background handling.

dash-dash/pyzmq,dash-dash/pyzmq,yyt030/pyzmq,caidongyun/pyzmq,yyt030/pyzmq,swn1/pyzmq,dash-dash/pyzmq,ArvinPan/pyzmq,caidongyun/pyzmq,Mustard-Systems-Ltd/pyzmq,yyt030/pyzmq,Mustard-Systems-Ltd/pyzmq,ArvinPan/pyzmq,ArvinPan/pyzmq,swn1/pyzmq,caidongyun/pyzmq,swn1/pyzmq,Mustard-Systems-Ltd/pyzmq