In this article, the second part of a series, we will continue discussing how TCP/IP works in tandem with client server applications. Then, we are going to use this knowledge to implement the server part of an example client-server application with Delphi. We are also going to look at the various components that are available to create network applications.
In this article we will continue discussing how TCP/IP works in tandem with client server applications. In the last article we discussed and saw how TCP/IP works and we have also learned how TCP/IP sends messages around a network. We also looked inside a typical TCP/IP message. Typically two computers on a network communicate through a sequence of numbers and acknowledgments as we've seen in the previous article. We'll start this article by showing you the "text" part of that example.
Below is a snippet of the actual text in the packet that was sent:
0010 03 e6 07 f1 40 00 80 06 6d cd c0 a8 00 01 c0 a8 ....@... m.......
03c0 73 74 69 63 73 52 65 73 70 6f 6e 73 65 3e 3c 2f sticsRes ponse></
03d0 53 4f 41 50 2d 45 4e 56 3a 42 6f 64 79 3e 3c 2f SOAP-ENV :Body></
03e0 53 4f 41 50 2d 45 4e 56 3a 45 6e 76 65 6c 6f 70 SOAP-ENV :Envelop
03f0 65 3e 0d 0a e>..
This is a typical view of a packet sent between two computers on a network. The data packet is sent in XML format wrapped in a SOAP envelope.
If data gets lost between the sending and receiving computers, TCP retransmits the packet until it reaches its destination or until a timeout limit is reached. Other features of TCP/IP let it recognize duplicate messages and get rid of them appropriately; it also detects whether a sending computer is transmitting too fast for the receiving computer. If it is, TCP/IP engages its flow control methods to slow down data transfer.