Process to process delivery is done in the transparent layer and for this two identifiers are required - IP address and part number. The IP address (which is universal) is required to select the host and the part number is required to select the process. Such a host can act as both a web server and an FTP (File Transfer Protocol) server if desired. In that case his IP address is the same but his party number is different. Socket address is a combination of IP address and part number. The figure below shows the socket address - two socket addresses required in the Transparent Layer protocol are the client socket address and the server socket address. The first identifies the client and the second identifies the server individually.