One of the crucial problems existed in information systems over the wide area networks(WAN) is information sharing and exchange. Due to the complexity of the wide area network as well as variances among different e-government application systems, it's difficult to implement the process of information exchange below the application layer defined in the hierarchy of Open System Interconnection(OSI) model. This paper proposes a new information exchange protocol based on overlay networks, which can provide a reliable transmission for both structured and unstructured data. In addition, it resumes transmission after break point and guarantees peer-to-peer security, with easy adaptability to different kinds of overlay networks. An e-government Information eXchange Platform is designed and implemented with respect to the proposed protocol, the transaction and adaptor mechanisms of which are also discussed. Furthermore, in order to improve the transmitting efficiency, a new method using sliding windows for transmitting SOAP message is presented in this paper, which would speed up SOAP message transmitting and thus provide an effective congestion-control strategy. Finally, simulation results are given for practical evaluation.