Hi Emmanuel, > If I run processes acting as SUB using ZMQ 4.0.3, will I have > compatibility problems between my PUB and SUB? > Is ZMQ 3.2.X compatible with ZMQ 4.0.3? Yes, fully compatible. The protocol has changed but ZMQ 4.0.3 will revert to using the ZMTP v2 protocol when it detects a ZMQ 3.2.x peer. -Pieter