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资源说明：A basic FTP client/ server for UNIX.
FTP client and server ========== #1. Protocol Specification The following section specifies the protocol for communication between the myftp client and the myftpd server. ##1.1. Transport Layer Protocol and Port Number The transport layer protocol used is TCP (transmission control protocol). The default port for the myftp protocol is 40903. ## 1.2. PUT Command Message Sequence and Format ##### 1. The client sends one message to the server to request a file upload. The message format is given below: * one byte opcode, which is ASCII character P, followed by * two-byte integer in two's compliment and in network byte order, which represents the length of the file name of the file sent to the server by * the sequence of ASCII characters representing the file name ##### 2. Once the server receives the message with the appropriate opcode, it responds with: * one byte opcode which is ASCII character P followed by * one-byte acknowledgement code, which is one of the following ASCII characters: * 0 - The server is ready to accept the named file * 1 - The server cannot accept the file because a file with the same name already exists in the target directory. * 2 - The server cannot accept the file because it cannot create the named file. * 3 - Server cannot accept due to miscellaneous error. ##### 3. Once the client receives the P message from the server and if the acknowledgement code is 0, it responds with the following message: * one byte opcode which is the ASCII character Q followed by * four byte integer in two's compliment and in network byte order which represents the length of the file followed by * a sequence of N bytes which is the content of the file. Files are transferred in 5120 byte blocks. If the file size is above 5120 bytes, multiple read/ writes must be constructed. ##### 4. Once the server receives the Q message from the client, the server responds with: * a one byte opcode which is ASCII character Q followed by * a one byte status code, which is one of the following ASCII characters: * 0 - File successfully written to disk * 1 - Server unable to write file to disk #### PUT Content ##### 1 Client Request > Opcode Length file name ##### 2 Server Response > Opcode Status ##### 3 Client Request > Opcode Length file contents ##### 4 Server Response > Opcode status #### PUT Example ##### 1 Client Request > P 7 foo.txt ##### 2 Server Response > P 0 ##### 3 Client Request > Q 1335 foo.txt contents ##### 4 Server Response > Q 0 ## 1.3. GET Command Message Sequence and Format ##### 1. The client sends a message to the server to request a file download. The message format is given below: * one byte opcode, which is ASCII character G, followed by * two-byte integer in two's compliment and in network byte order, which represents the length of the file name of the file downloaded from the server by * the sequence of ASCII characters representing the file name ##### 2. Once the server receives the message with the appropriate opcode, it responds with: * one byte opcode which is ASCII character G followed by * one-byte acknowledgement code, which is one of the following ASCII characters: * 0 - The server is ready to send the named file to the client * 1 - The file name specified does not exist * 2 - File permissions error * 3 - The server cannot send file due to miscellaneous error. ##### 3. Once the client receives the G message from the server and if the acknowledgement code is 0, it issues the following message: * one byte opcode which is the ASCII character H followed by * four byte integer in two's compliment and in network byte order which represents the length of the file followed by * a sequence of N bytes which is the content of the file ##### 4. Once the server receives the H message from the client, the server responds with: * a one byte opcode which is ASCII character H followed by * a one byte status code, which is one of the following ASCII characters: * 0 - File transfer initiated successfully * 1 - File name specified does not exist * 2 - File permission error * 3 - The server encountered a miscellaneous error * four byte integer in two's compliment and in network byte order which represents the length of the file followed by * a sequence of N bytes which is the content of the file. Files are transferred in 5120 byte blocks. If the file size is above 5120 bytes, multiple read/ writes must be constructed. #### GET Content ##### 1 Client Request > opcode length file name ##### 2 Server Response > opcode status ##### 3 Client Request > opcode length file name ##### 4 Server Response > opcode status length file content #### GET Example ##### 1 Client Request > G 7 bar.txt ##### 2 Server Response > G 0 ##### 3 Client Request > H 7 bar.txt ##### 4 Server Response > H 0 1400 bar.txt file contents ## 1.4. PWD Command Message Sequence and Format ##### 1. The client sends a message to the server to request the current directory of the server. The message format is given below: * one byte opcode, which is ASCII character W ##### 2. Once the server receives the message with the opcode W, it responds with: * one byte opcode, which is ASCII character W, followed by * two-byte integer in two's compliment and in network byte order, which represents the length of the path returned in the result * a one byte status code containing one of the following ASCII characters: * 0 - Command completed successfully * 1 - Miscellaneous error * a sequence of ASCII characters representing the current path #### PWD Content ##### 1 Client Request > opcode ##### 2 Server Response > opcode length status path #### PWD Example ##### 1 Client Request > W ##### 2 Server Response > W 16 0 /home/user/temp ## 1.5. DIR Command Message Sequence and Format ##### 1. The client sends a message to the server to request the contents of the current directory of the server. The message format is given below: * one byte opcode, which is ASCII character D ##### 2. Once the server receives the message with the opcode D, it responds with: * one byte opcode, which is ASCII character D followed by * two-byte integer in two's compliment and in network byte order, which represents the length of the list of files * a one byte status code containing one of the following ASCII characters: * 0 - Navigated directory successfully * 1 - Miscellaneous error * a sequence of ASCII characters representing the current directory contents #### DIR Content ##### 1 Client Request > opcode ##### 2 Server Response > opcode length status list of files #### DIR Example ##### 1 Client Request > D ##### 2 Server Response > D 23 0 foo.txt bar.txt baz.txt ## 1.6. CD Command Message Sequence and Format ##### 1. The client sends a message to the server to request a change of the host directory. The message format is given below: * one byte opcode, which is ASCII character C * a two-byte integer in two's compliment and in network byte order, which represents the length of the directory to navigate to * a sequence of ASCII characters representing the host directory to navigate to ##### 2. Once the server receives the message with the opcode C, it responds with: * one byte opcode, which is ASCII character C followed by * a one byte status code containing one of the following ASCII characters: * 0 - Navigated to given directory successfully * 1 - Miscellaneous error #### CD Content ##### 1 Client Request > opcode length directory ##### 2 Server Response > opcode result #### CD Example ##### 1 Client Request > C 16 /home/user/temp ##### 2 Server Response > C 0
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