Understanding of FTP protocol

Plan complete

1.ftp Agreement understanding

2. Active mode and passive mode

3. Packet capturing analysis of interaction process

4.C++ Code module （ transplant ） Harmony and reality

How to distinguish between simple and complex communication protocols in the network ？ such as ,

When the client accesses the server for communication , Use only ” A connection ” To transmit data , It can be understood as a simple protocol .  for example HTTP,SSH,TELNET etc.

Reverse the above , The communication between client and server is , A protocol that requires multiple connections to complete an application , It's a complex agreement

such as ftp That's all. , So understand ftp.

2.FTP Working mode of

FTP There are two kinds of working modes of , Passive mode and active mode .

（1） Passive mode