The difference between TCP/IP, Http, and socket

The network is divided from bottom to top:

The physical layer, the data link layer, the network layer, the Transport layer, the session layer, the presentation layer, and the application layer.

For example, the IP protocol corresponds to the network layer, the TCP protocol corresponds to the transport layer, and the HTTP protocol corresponds to the application layer;

The three are inherently non-comparable, and sockets are encapsulated and applied to the TCP/IP protocol (at the programmer level).

It can also be said that:

• TPC/IP protocol is a Transport layer protocol, which mainly solves how data is transmitted in the network.

• HTTP is an application-layer protocol that primarily addresses how data is packaged.

regarding the relationship between TCP/IP and HTTP protocol , the network has a relatively easy to understand introduction:

When we transmit data, we can use only the (Transport Layer) TCP/IP protocol, but in that case, the data content cannot be recognized without the application layer. If you want to make the transferred data meaningful, you must use the application-layer protocol.

There are many application layer protocols, such as HTTP, FTP, Telnet, etc., and you can define the application layer protocol yourself.

The web uses the HTTP protocol as an application-layer protocol to encapsulate HTTP text information and then send it to the network using TCP/IP as the Transport layer protocol.

　

And what we usually say the most socket is what, in fact, the socket is the TCP/IP protocol encapsulation, the socket itself is not a protocol, but a call interface (API).

　　

With the socket, we can use the TCP/IP protocol. In fact, the socket is not necessarily associated with the TCP/IP protocol. The socket programming interface is designed to adapt to other network protocols as well.

So, the advent of sockets just makes it easier for programmers to use the TCP/IP protocol stack, which is an abstraction of the TCP/IP protocol, thus forming some of the most basic function interfaces we know, such as Create, listen, connect, accept, send, Read and write, and so on.

The network has a section on the socket and TCP/IP protocol relationship is relatively easy to understand:

TCP/IP is just a protocol stack, just like operating system operation mechanism, must be implemented specifically, but also to provide external operating interface.

This is like the operating system will provide a standard programming interface, such as the Win32 programming interface, TCP/IP should also provide the interface for programmers to do network development, this is the socket programming interface.

About the TCP/IP protocol related knowledge, with "profound" I think not too, just check the online about this kind of information and books only the number of documents to know. This I am going to buy some classic books (such as "TCP/IP Detailed: Volume One, Volume II, Volume three") to learn.

Today, we summarize some of the knowledge based on TCP/IP protocol-based applications and programming interfaces, which is just a lot of HTTP and sockets.

　　

CSDN has a comparative image of the description: HTTP is a sedan, provides a package or display the specific form of data; The socket is the engine that provides the ability to communicate over the network.

　　

In fact, the transport layer TCP is based on the network layer of IP protocol, and the application layer of the HTTP protocol is based on the transport layer of the TCP protocol, and the socket itself is not a protocol, as mentioned above, it just provides a TCP or UDP programming interface.

　　

Here are some of the important concepts that are often encountered in a written test or interview and are summarized here.

One, what is the three-time handshake for a TCP connection

First handshake: The client sends a SYN packet (SYN=J) to the server and enters the Syn_send state, waiting for the server to confirm;

　　

Second handshake: The server receives the SYN packet, it must confirm the customer's SYN (ACK=J+1), and also send itself a SYN packet (syn=k), that is, the Syn+ack packet, when the server enters the SYN_RECV state;

　　

Third handshake: The client receives the server's Syn+ack packet, sends the acknowledgment packet ack (ACK=K+1) to the server, the packet is sent, the client and the server enter the established state, and the handshake is completed three times.

　　

The data is not included in the packets that are delivered during the handshake, and the client and server formally begin transmitting the data after the three handshake is complete.

　　

Ideally, once a TCP connection is established, the TCP connection is maintained until either side of the communication actively closes the connection.

　　

When disconnected, both the server and the client can initiate a request to disconnect the TCP connection, and the disconnection process requires a "four handshake" (the process is not fine-grained, that is, the server interacts with the client and finally determines the disconnection)

Ii. steps to establish a network connection using a socket

Establishing a socket connection requires at least one pair of sockets, one running on the client, called Clientsocket, and the other running on the server side, called ServerSocket.

　　

The connection between sockets is divided into three steps: Server listening, client request, connection acknowledgement.

　　

1, Server monitoring: Server-side sockets do not locate the specific client sockets, but in the status of waiting for the connection, real-time monitoring network status, waiting for the client connection request.

　　

2, client request: Refers to the client socket to make a connection request, to connect to the target is the server-side socket.

　　

To do this, the client's socket must first describe the socket of the server it is connecting to, indicate the address and port number of the server-side socket, and then make a connection request to the server-side socket.

　　

3. Connection confirmation: When the server side socket is heard or received the connection request of the client socket, it responds to the request of the client socket, establishes a new thread, sends the description of the server end socket to the client, and once the client confirms the description, the two sides formally establish the connection.

　　

While the server-side socket continues to be in the listening state, it continues to receive connection requests from other client sockets.

Third, the characteristics of HTTP links

The HTTP protocol, the Hypertext Transfer Protocol (hypertext Transfer Protocol), is the foundation of Web networking and one of the most commonly used protocols for mobile networking, an application built on the TCP protocol.

　　

The most notable feature of an HTTP connection is that each request sent by the client requires a server loopback response, and the connection is actively released after the request has ended. The process from establishing a connection to closing a connection is called a "one-time connection."

Iv. differences between TCP and UDP

(Most of the exams are done.) It's getting rotten. I think--\\)

• TCP is a link-oriented, although the network's insecure instability determines how many times the handshake can not guarantee the reliability of the connection, but the TCP three handshake at a minimum (in fact, to a large extent guaranteed) to ensure the reliability of the connection;

• And UDP is not connection-oriented, UDP transmission data before the connection with the other, the docking received data does not send a confirmation signal, the sender does not know whether the data will be received correctly, of course, there is no need to resend, so that UDP is a non-connected, unreliable data transmission protocol.

　　

• Also due to the characteristics of 1, so that the cost of UDP more small data transmission rate is higher, because there is no need to send and receive data confirmation, so UDP real-time better.

　　

Knowing the difference between TCP and UDP, it is not difficult to understand why the use of TCP Transport protocol MSN than the use of UDP QQ transmission files slow. But it cannot be said that QQ communication is not safe, because the programmer can manually authenticate UDP data transmission, such as the sender of each packet number and then by the receiver to verify AH what.

　　

Even so, UDP does not have a TCP-like "three-time handshake" on the package of the underlying protocol to achieve the transmission efficiency that TCP cannot achieve.

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The difference between TCP/IP, Http, and socket