Synchronous web services are the services where the client or the user gets the response of his request immediately and is also called as Synchronous is request-response operation (SOAP). Attachments API for JavaTM (SAAJ) are generally used for developing this mode of communication. Whereas, asynchronous web service is commonly called as a one way operation where the user needs to wait for the response. Generally in this mode of communication, the client sends his request in XML format and the response is received over a fixed period of time.