Some thoughts on port forwarding program

 If I want to write a port forwarding program , Similar to the multi person chat room , Under a LAN ,
 Everyone sends a message to the server , Then the server will forward this message to the corresponding person .
 therefore socket Communication is no longer between individuals , It's communication between people .
 There is no need to reopen one every time socket, But the use of socket I / O stream .
 So how should it be written ？

 First , An independent network is set for each communication device under the LAN IP,
 then , Maintain a dynamic array on the server side , The array contains the data that has been connected to the server socket object ,
 Accurately speaking , In this way socket object 、 Each represents a client .

 Each one is established with the server side socket Communication client , Both threads are open , One is responsible for outputting the character stream ,
 One is responsible for receiving the character stream .

 In the server-side dynamic array , You need to keep looking through the loop IP、 Forward messages , How to do it? ？

 In the information sent by the client , Containing the target object IP And information ,
 After receiving the information on the server , Let each element in the maintained dynamic array (socket object ) Go to 
 Query the information sent IP Is it the same as your own , If they are the same, the character stream is output .

 This is actually an abstraction , On the server side socket The shadow of communication , Forward messages through such shadows ,
 Disadvantages: high consumption of hardware resources , Every time a client joins the group chat , Then the server side needs to add a socket shadow ,
 At the same time the socket The shadow also needs to traverse other socket shadow . This is actually very resource consuming , Multiplicative relation .
 For example, communication between two people is 2 * 2, So ten person correspondence is 10 * 10.

 Such a network structure is actually understandable .

 What if it is between two network segments ？

 For example, my device is wired at the same time