Web Services generally uses HTTP or HTTPS protocol over the application layer of computer network where one application transfer data or send requests as XML or JSON and receives the response which is processed by the client application as a web service irrespective of underlying software platform, architecture and technology.
All the standard web services work using the following components
Web service enables communication among various applications installed on different devices by using open standards as discussed below:
The purpose of Web Service testing is to verify that all of the Web Service APIs published by your application operate as expected. Web Service API testing requires that you test using all the expected data formats and input parameters.
SOAP: It is a standard protocol defined by the W3C Standard for sending and receiving web service requests and responses.
SOAP uses the XML format to send and receive the request and hence the data is platform independent data. SOAP messages are exchanged between the provider applications and receiving application within the SOAP envelops
As SOAP uses the simple http transport protocol, its messages are not got blocked by the firewalls.
Rest: It is an architecture that generally runs over HTTP. The REST style emphasizes the interactions between clients and services, which are enhanced by having a limited number of operations. REST is an alternative to SOAP (Simple Object Access Protocol) and instead of using XML for request REST uses simple URL in some cases.