Yyds dry goods inventory TCP & UDP

Connection oriented

• TCP: Reliable transmission 、 Connection oriented ---> Slow speed , High accuracy
• UDP: Unreliable transmission 、 Non connection oriented ---> Fast , Poor accuracy
• If the four layers of an application layer protocol are used TCP port , Then before the formal data message transmission , You need to establish a connection first . Data can only be transferred after the connection is established .
• Three handshakes : Connection oriented high-level protocols need to establish a connection before formally transmitting data , The process of establishing a connection requires sending three messages back and forth , We call the process of establishing a connection three handshakes

Three handshakes

• The client sends syn package (syn=j) To the server , Request to establish a connection

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        At this stage ,TCP The message contains ：  Source port 、 Destination port 、SYN identification 
      
      
      
      

       
       
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• Server received SYN package , Must confirm customer's SYN(ack=j+1), At the same time, I also send a SYN package (syn=k), namely SYN+ACK package

• Client receives server's SYN+ACK package , Send confirmation package to server ACK(ack=k+1)