 7.     FTP_________________________253

U: STOR /home/images/first.my
S: 550 Access denied
U: QUIT

       FTP ( -
  ,   . 7.2)   . 7.3.

User-PI (U) <-> Server-l (S1)        User-PI (U) <^ Server2 (S2)

U > S1 : Connect                  U > S2 : Connect
U -> S1 : PASV
S1 > U : 227 Entering Passive Mode.
A1,A2,A3,A4,a1,a2

U -> S2 : PORT A1, A2, A3, A4, a1, a2
S2-- U : 200 Okay
U -> S1 : STOR ...                 U -> S2 : RETR . ..

S1  S2 : Connect. ..
. 7.3.        FTP

 TFTP  SFTP

FTP-   " ": SFTP  Simple FTP  TFTP 
Trivial FTP.

TFTP-      .  
   UDP    
    ,  ,   
. TFTP         -
.           
,    8-   -
    Internet.

     UDP,  TFTP
        -
,        . . 
        TCP.

TFTP    :

1. Read request (RRQ)    .

2. Write request (WRQ)    .

3. Data (DATA)   .

4. Acknowledgment (ACK)  .

5. Error (ERROR)  .