TCP IP Illustrated

The command has been accepted but another command

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Unformatted text preview: ts%20and%20Settings/bigini/Docum.../homenet2run/tcpip/tcp-ip-illustrated/ftp_file.htm (5 of 24) [12/09/2001 14.47.49] Chapter 27. FTP: File Transfer Protocol Each of the three digits in the reply code has a different meaning. (We'll see in Chapter 28 that the Simple Mail Transfer Protocol, SMTP, uses the same conventions for commands and replies.) Figure 27.3 shows the meanings of the first and second digits of the reply code. Reply Description 1yz Positive preliminary reply. The action is being started but expect another reply before sending another command 2yz Positive completion reply A new command can be sent 3yz Positive intermediate reply. The command has been accepted but another command must be sent 4yz Transient negative completion reply The requested action did not take place, but the error condition is temporary so the command can be reissued later. 5yz Permanent negative completion reply. The command was not accepted and should not be retried. X0z Syntax errors. x1z Information. x2z Connections. Replies referring to the control or data connections. x3z Authentication and accounting. Replies for the login or accounting commands. x4z Unspecified. x5z Filesystem status. Figure 27.3 Meanings of first and second digits of 3-digit reply codes. The third digit gives additional meaning to the error message. For example, here are some typical replies, along with a possible message string. q q q q q q q q q 125Data connection already open; transfer starting. 200 Command OK. 214 Help message (for human user). 331 Username OK, password required. 425 Can't open data connection. 452 Error writing file. 500 Syntax error (unrecognized command). 501 Syntax error (invalid arguments). 502 Unimplemented MODE type. Normally each FTP command generates a one-line reply For example, the QUIT file:///D|/Documents%20and%20Settings/bigini/Docum.../homenet2run/tcpip/tcp-ip-illustrated/ftp_file.htm (6 of 24) [12/09/2001 14.47.49] Chapter 27. FTP: File Transfer Protocol command could generate the reply: 221 Goodbye. If a multiline reply is needed, the first li...
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