A Pushlet IM method for pushing a message from a first client device to a second client device includes the steps of: providing a Java-based web service; receiving a message from the first client device, the message including information of a recipient entity; verifying identity of a sender entity who intends to send the message to the recipient entity using the first client device; and creating a thread according to the information of the recipient entity for pushing the message to the second client device that is associated with the recipient entity.