FTP stands for File Transfer Protocol. The purpose of an FTP program is to enable computer users to copy (transfer) files from one computer to another.
A computer protocol is a set of rules that determines how computers communicate with each other. These rules are similar to rules that humans use for communicating in special circumstances to ensure that all communications are received properly. For example, when two people are communicating using old-style walkie-talkies only one communication channel is used. The walkie-talkies are normally configured with a switch that may be placed in either the talk or the listen position. Therefore it is important that the two people do not try to talk at the same time otherwise neither will be able to hear what the other is saying. Some walkie-talkies are equipped with a buzzer to facilitate initiating a conversation. We will assume that we are using the bare-bones model without a buzzer. There are rules for communicating using walkie-talkies. These rules are defined by a protocol as follows.
Walkie-Talkie Protocol
To contact another person (initiate a connection) a person must
Place the communication control into the talk position,
say "Come in, <person's name>, OVER" then
place the communication control into the listen position.
The person being contacted, upon hearing the word OVER places the communication control into the talk position and accepts control of the communication line.
If the person initiating a connection hears no response for 30 seconds, he/she repeats the steps above.
When a person hears an attempted communication contact he/she
places the communication control into the talk position,
says "Go Ahead, OVER" and then
places the communication control into the listen position.
Whoever is talking remains in control of the communication line until he/she releases it by saying "OVER".
To terminate a connection
A person must first have control of the communication line then
the person wishing to terminate the connection says "OVER and OUT" then
places the communication control into the listen position.
If the person to whom you are communicatng terminates the connection by saying "OVER and OUT" leave the communication control into the listen position.
When the walkie-talkie is not in use the communication control should remain in the listen position.
It is worth noting how meticulous the above protocol is. This detail is necessary for successful communication. Computer protocols must be so specific that a computer can carry out the instructions without human intervention.
As an exercise review the walkie-talkie protocol above and
Determine if or why each item is required.
Determine if the prortocol as stated above is flawless if both persons follow the rules precisely. Or can there be
miscommunication
(for ex. conversation is misunderstood because only a portion is received.)
connection failure
(an attempted connection between two accessible individuals fails because of a flaw in the protocol.)
or
termination failure?
(one person thinks the communication is terminated but the other does not.)
Describe your findings in a text file. Call the text file WalkTalkPro.txt and FTP (copy) the file to your studentserv server account.
Although it is much more complex, the File Transfer Protocol serves a similar purpose and is similar in several other respects to the walkie-talkie protocol above. Fortunately you do not need to know very much abot the FTP protocol to use FTP to copy files over a network. You do need to understand how to use an FTP program and practice sending files in order to be proficient.
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