• 想在ESP32上用TCP来实现ftp服务器，抓一下ftp通信包分析一下。
• 总的来说就是两个TCP通道，一个命令通道，一个数据通道；
• 数据通道只有在遍历目录、下载、上传的时候才开启，其余时候均不开启；
• 主要就是协议对接好就OK咯。

USER

• USER slim
• 331 Password required for slim\r\n

PASS

• PASS root
• 230 Logged on\r\n

PWD

• PWD\r\n
• 257 “/” is current directory.\r\n

CWD

• CWD .\r\n
• 250 CWD successful. “/” is current directory.\r\n

LIST

• LIST\r\n
• 150 Opening data channel for directory listing of “/”\r\n
• data通道：目录内容
• 226 Successfully transferred “/”\r\n

NLST

• NLST\r\n
• 150 Opening data channel for directory listing of “/”\r\n
• data通道：目录内容
• 226 Successfully transferred “/”\r\n

MLSD

• MLSD\r\n
• 150 Opening data channel for directory listing of “/”\r\n
• data通道：发送目录信息
• 226 Successfully transferred “/”\r\n

TYPE

• TYPE A\r\n
• 200 Type set to A\r\n

STOR

• STOR /ftp_dir.c\r\n
• 150 Opening data channel for file upload to server of “/ftp_dir.c”\r\n
• data通道：发送文件内容
• 226 Successfully transferred “/ftp_dir.c”\r\n

1. STOR文本

2. STOR图片

RETR

• RETR /test_buff.c\r\n
• 150 Opening data channel for file download from server of “/test_buff.c”\r\n
• data通道：传输数据内容
• 226 Successfully transferred “/test_buff.c”\r\n

1. RETR文本

2. RETR图片

PORT

• PORT 127,0,0,1,210,140\r\n
• 200 Port command successful\r\n

PASV

• PASV\r\n
• 227 Entering Passive Mode (127,0,0,1,202,112)\r\n

• 异常情况

QUIT

• QUIT\r\n
• 221 Goodbye\r\n

DELE

• DELE /tmp.exe\r\n
• 250 File deleted successfully\r\n

MKD

• MKD dir1\r\n
• 257 “/dir1” created successfully\r\n

RMD

• RMD dir3\r\n
• 250 Directory deleted successfully\r\n

CDUP

• CDUP\r\n
• 200 CDUP successful. “/test.c” is current directory.\r\n

RNFR

• RNFR dir-1111\r\n
• 350 Directory exists, ready for destination name.\r\n

RNTO

• RNTO dir-new\r\n
• 250 file renamed successfully\r\n

FEAT

• FEAT
• 211-Features:\r\n
  MDTM\r\n
  REST STREAM\r\n
  SIZE\r\n
  MLST type*;size*;modify*;\r\n
  MLSD\r\n
  UTF8\r\n
  CLNT\r\n
  MFMT\r\n
  EPSV\r\n
  EPRT\r\n
  211 End\r\n
  [Current working directory: ]

SIZE

• SIZE /test_buff.c\r\n
• 213 5245\r\n

SYST

• SYST\r\n
• 215 UNIX emulated by FileZilla\r\n

NOOP

• NOOP\r\n
• 200 OK\r\n

ABOR

MODE

HELP

XPWD（不支持）

MDTM（不支持）

APPE（不支持）

AUTH （不支持）

最后记录一下响应码：