In the past two months, this column has introduced some of the functions necessary for writing networked programs. We’ve been throwing around terms like TCP, UDP, IP, and others without any real description of what they mean. This month, you should gain a better understanding of these abbreviations and exactly what is going on when they are used to communicate between machines. With this knowledge, you will be better equipped to determine exactly which protocol is appropriate for your applications — for instance, why UDP is often used for broadcast-style transmissions, while TCP is used for transactions.
In the past two months, this column has introduced some of the functions necessary for writing networked programs. We’ve been throwing around terms like TCP, UDP, IP, and others without any real description of what they mean. This month, you should gain a better understanding of these abbreviations and exactly what is going on when they are used to communicate between machines. With this knowledge, you will be better equipped to determine exactly which protocol is appropriate for your applications — for instance, why UDP is often used for broadcast-style transmissions, while TCP is used for transactions.
Before jumping into the different protocols that make up network communication, let’s take a look at how a protocol actually becomes a standard. The documents describing the various network protocols are called RFCs (Request for Comments). RFCs were started in 1969 as a set of documents to describe the various protocols pertaining to the Internet. It is easy to find RFCs for different protocols online at http://www.rfc-editor.org/.
RFC 791 describes the Internet Protocol (IP), RFC 768 describes the User Datagram Protocol (UDP), and RFC 793 describes the Transmission Control Protocol (TCP). RFCs are used to describe many higher-level protocols that you are probably more familiar with. For example, FTP is described in RFC 959, HTTP 1.0 is described in RFC 1945, and the telnet protocol is described in RFC 854.
When writing an application like an FTP client or server, the RFC describing the protocol should be the…
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