How does the TCP server handle multiple client connections on one port (one-to-one or one to many)

We often see that ,TCP It's a one-to-one two-point service ,UDP Support one-to-one 、 One to many 、 Many to many interactive communication . But use Tcp Tool communication , One Tcp The server can connect multiple Tcp client . So is there a conflict between one-to-one and one to many here ？

Not at all . One on one means Tcp Connect , What is? Tcp Connect , Paste directly here Kobayashi great God The explanation of .

The combination of these control information can be called connection . So one-to-one means that a combination of control information can only target one Tcp client .

that Tcp Tools How to realize one to many communication ？

I used tools here to build a TCP Server side (5679) And two TCP client (6159 and 6259).
I see someone on the Internet explaining this problem is , be supposed to tcp When the server handles multiple connections , A new port is created internally to handle . wrong ！！！ Let's take a look at windows On tcp Socket information is known

Socket here refers to the socket of communication object IP Address 、 Port number 、 Information such as the progress status of communication operation . A line in the figure is equivalent to a socket . Why do you need the socket concept , When it comes to one to many implementation .

You can see tcp The port of the server has always been 5679, No other ports are displayed , therefore tcp The server has only one port ！！！

that tcp How does the server handle multi-user connections ？

Say first conclusion , Server side Socket The program handles . therefore TCP It's one-on-one ,Socket One to many ！

Server side socket The program is divided into two modules , That is, the waiting connection module and the module responsible for communicating with the client . When the server program starts and reads the configuration file to complete the initialization operation , Will run the wait to connect module . This module creates sockets , Then enter the suspended state of waiting for connection . Next , When When the client initiates a connection , This module will resume operation and accept connections , Then start the client communication module , And hand over the socket that completes the connection . Next , The client communication module will use the connected socket to communicate with the client , After the communication is over , This module exits .


After copying a new socket , It turned out that the one in waiting company What will happen to sockets connected to state ？ In fact, it will continue to exist in the state of waiting for connection , When called again accept, The client connects the package to Time of arrival , It can perform the accept connection operation again . After accepting the new connection , Just like before , The protocol stack will be used for this socket waiting for connection Make a new copy of the word , Then let the client connect to the new replica socket .

The more detailed principle is shown in the figure below

It is highly recommended to see 《 How is the network connected 》. Don't say anything else. If you have problems, you can communicate more .