Why is the TCP handshake just 3 times?

Why? TCP The handshake was just 3 And then ？

because 3 The second handshake is the minimum number of interactions that can let both parties know that the other party has the ability to send and receive

As shown in the figure above :

1. The first 1 After a handshake ：Client The message of is Server receive

   Server Only certain Client The data sent can reach Server End

   Serevr It can correctly receive data from the opposite end

2. The first 2 After a handshake ：

   Client Received data from the opposite end , So in Client From the perspective of ：

   Client The receiving capacity is normal

   Client Normal sending capacity （ Because the first handshake is normal, I will receive the confirmation ）

   Server The receiving capacity is normal （ Because the second handshake confirmation will be received only when the reception is normal ）

   Server Normal sending capacity

3. The first 3 After a handshake ：

   Server received Client There was a confirmation , So from Server Perspective ：

   Client The receiving capacity and sending capacity of are normal

   Server The receiving and sending capacity of the is normal

Because both sides know that the receiving and sending capacity of the other side is ok 了 , So you can happily establish a connection