Detailed explanation of socket usage in php

The original English meaning of socket is "hole" or "socket". As the process communication mechanism of BSD UNIX, the latter meaning is taken. Used to describe IP addresses and ports, and is the handle of a communication chain. Hosts on the Internet generally run multiple service software and provide several services at the same time. Each service opens a Socket and binds it to a port. Different ports correspond to different services

PHP socket programming is relatively difficult to understand. However, we only need to understand a few socket functions It shouldn’t be difficult to understand the relationship between them and the roles they play. In the author’s opinion, socket programming is actually about establishing a client and server for a network service, which is similar to the client and service of mysql. The client and server are the same. As long as you understand what the client and server of MySQL are about, you should be able to understand what I am going to talk about below.

Regarding the network protocols involved in socket programming, such as TCP, UDP, socket three-way handshake, etc., there are very detailed explanations of these network protocols on the Internet. I will not go into them here. I will just cut a socket to create a socket. The process map of the connection is to let you see:

# This picture is what I have worked hard from others, you must look good, at the same time, here I am here I would also like to express my gratitude to the author whose screenshot was stolen from me. I apologize for stealing your pattern. I hope you don’t care about it. I am too lazy to draw pictures (actually it means I am not confident in my drawing skills, haha).

How does the socket establish a connection? As mentioned above, the process of establishing a connection is essentially the same as the connection between mysql client and server. The difference between it and mysql is that the server and client of mysql have been edited for us, we just need to apply it. However, the critical moment has come. Socket does not provide us with anything. The only thing it provides us is: dozens of socket functions.

The implication is that socket programming requires us to create the server and client ourselves. In other words, ``socket programming``--it requires us to create a server and client similar to mysql. terminal application.

Speaking of which, I would like to ask, do you think this socket is a headache? It neither creates a server nor a client for us to apply. We have to use the socket function ourselves and create our own network protocol socket application. Doesn't this give you a headache? There's nothing you can do about the headache. If you need your own application, you still have to deal with sockets. Haha, this is just a digression, I won’t say much, let’s get to the point.

Before you are confused by socket programming, I will let you take a look at several key functions of socket and explain their respective functions to you. Otherwise, if someone who has no foundation in socket programming reads this, I'm afraid that after reading it, you will decisively skip this article and develop a phobia about sockets from now on. Haha, I said more.

The key function of socket 1:

socket_create($net parameter 1, $stream parameter 2, $protocol parameter 3)

Function: Create a socket socket, To put it bluntly, it is a network data flow.

Return value: a socket, or false, an E_WARNING warning is issued for parameter errors

The PHP online manual makes it clearer:

socket_create creates and returns a Socket, also called a communication node. A typical network connection consists of 2 sockets, one running on the client side and the other running on the server side.

The above sentence is copied from the PHP online manual. Do you see that the meaning here is exactly the same as the client and server that I mentioned repeatedly above? hehe.

　　Parameter 1 is: network protocol,

　　What are the network protocols? Its options are the following three:

AF_INET: IPv4 network protocol. Both TCP and UDP can use this protocol. This is generally used, you know.

　AF_INET6: IPv6 network protocol. Both TCP and UDP can use this protocol.

AF_UNIX: Local communication protocol. High-performance and low-cost IPC (Inter-Process Communication).

Parameter 2: Socket stream, options are:

SOCK_STREAM SOCK_DGRAM SOCK_SEQPACKET SOCK_RAW SOCK_RDM.

Only the first two are explained here:

SOCK_STREAM TCP protocol socket.

　　SOCK_DGRAM　 UDP protocol socket.

For more information, please link here: http://php.net/manual/zh/function.socket-create.php

Parameter 3: protocol, options are:

SOL_TCP: TCP protocol.

SOL_UDP: UDP protocol.

It can be seen from here that the second parameter and the third parameter of the socket_create function are actually related.

For example, if your first parameter uses the IPv4 protocol: AF_INET, and then the second parameter uses the TCP socket: SOCK_STREAM,

Then the third parameter must be used SOL_TCP, this should not be difficult to understand.

As for TCP protocol sockets, of course you can only use the TCP protocol, right? If you use UDP sockets, I won’t say how to choose the third parameter, haha, you know.

Key function 2:

socket_connect($socket parameter 1, $ip parameter 2, $port parameter 3)

Function: connect a socket, the return value is true or false

Parameter 1: function return value of socket_create

Parameter 2: ip address

Parameter 3: Port number

Key function 3:

　　socket_bind($socket parameter 1, $ip parameter 2, $port parameter 3)

　　 Function: Bind a socket, the return value is true or false

　　 Parameters 1: function return value of socket_create

Parameter 2: ip address

Parameter 3: Port number

Key function 4:

socket_listen($socket parameter 1,$backlog Parameter 2)

Function: Listen to a socket, the return value is true or false

Parameter 1: The function return value of socket_create

Parameter 2: Maximum number of listening sockets

Key function 5:

socket_accept($socket)

Function: Receive the resource information of the socket and return the socket successfully Information resources, failure is false

Parameters: function return value of socket_create

Key function 6:

socket_read($socket parameter 1, $length parameter 2)

Function: Read the resource information of the socket,

Return value: Successfully convert the socket resource into string information, failure is false

Parameter 1: socket_create or The function return value of socket_accept

Parameter 2: The length of the read string

Key function 7:

socket_write($socket parameter 1, $msg parameter 2, $ strlen parameter 3)

Function: Write data into the socket

Return value: Return the byte length of the string if successful, false

on failure Parameter 1: The function return value of socket_create or socket_accept

Parameter 2: String

Parameter 3: The length of the string

Key function 8:

socket_close($ socket)

Function: Close the socket

Return value: Return true on success, false on failure

Parameters: Function return value of socket_create or socket_accept

These eight functions are the core functions of socket. Here are two more important functions

socket_last_error($socket). The parameter is the return value of socket_create. Its function is to obtain the last error code of the socket. Number, return value socket code

　　socket_strerror($code), the parameter is the return value of the socket_last_error function, obtain the string information of the code, the return value is the socket error information

These two functions are still very important in socket programming. When writing socket programming, I think you still have to make use of them, especially for novices. They can be used for debugging

　　　That’s the code, pay attention, please read my comments carefully, comments are very important, comments are very important, comments are very important, important things should be shouted three times, haha.

Server-side script, D:\vhost\test\socket\server_socket.php

 Tip: Please note that the execution order of the three functions socket_bind, socket_listen, and socket_accept above cannot be changed. That is to say
　　You must first execute socket_bind, then socket_listen, and finally execute socket_accept
 Client script, D:\vhost\test\socket\client_socket.php
 1, "usec" => 0));
   //发送套接流的最大超时时间为6秒
  socket_set_option($socket, SOL_SOCKET, SO_SNDTIMEO, array("sec" => 6, "usec" => 0));
  /****************设置socket连接选项，这两个步骤你可以省略*************/

  //连接服务端的套接流，这一步就是使客户端与服务器端的套接流建立联系
  if(socket_connect($socket,'127.0.0.1',8888) == false){
    echo 'connect fail massege:'.socket_strerror(socket_last_error());
  }else{
    $message = 'l love you 我爱你 socket';
    //转为GBK编码，处理乱码问题，这要看你的编码情况而定，每个人的编码都不同
    $message = mb_convert_encoding($message,'GBK','UTF-8');
    //向服务端写入字符串信息

    if(socket_write($socket,$message,strlen($message)) == false){
      echo 'fail to write'.socket_strerror(socket_last_error());

    }else{
      echo 'client write success'.PHP_EOL;
      //读取服务端返回来的套接流信息
      while($callback = socket_read($socket,1024)){
        echo 'server return message is:'.PHP_EOL.$callback;
      }
    }
  }
  socket_close($socket);//工作完毕，关闭套接流
 How to test these two scripts? 
 First, open the DOS window of Windows, which is the cmd black window. Then, run php D:\vhost\test\socket\server_socket.php, 
 Let the black window of the server continue to run. ,
 Secondly, the php client script can be run through the browser, or you can open a cmd black window to run
　 php D:\vhost\test\socket\client_socket.php
 Please note here: the php running name must be added to the Windows environment variable. If you don’t know how to add it, 
 Please enter the php running command directory and run it with an absolute command. You can also use Baidu to add the php command Add it to the environment variable
This is my situation, your file address may be different from mine, please operate according to your address, otherwise, you will be responsible for the consequences, haha
 As mentioned above, socket programming requires a server to communicate, so the black window on the server must be kept open. 
 Postscript: 
socket_set_option($socket parameter 1, $level parameter 2, $optname parameter 3, $optval parameter 4)
The function of this function is to set The interface sets the data flow options, which is also a very important function. 
Parameter 1: The function return value of socket_create or socket_accept
Parameter 2: SOL_SOCKET, it seems that this is the only option
Parameter 3 and parameter 4 are related,
 
 Parameter 3 can be: SO_REUSEADDR SO_RCVTIMEO S0_SNDTIMEO

Explain: 
SO_REUSEADDR It allows the socket port to be used again immediately after it is released
 If parameter 3 is this, parameter 4 can be true or false
SO_RCVTIMEO　It is the maximum timeout time of the socket's receiving resource
SO_SNDTIMEO　It is the maximum timeout time of the socket's sending resource 
 If parameter 3 is these two, then parameter 4 is an array array('sec'=>1,'usec'=>500000)

 Array They all set the maximum timeout time. However, one is in seconds and the other is in microseconds. They have the same effect.

The above is the entire content of this article. I hope it will be useful to everyone. Helps. 


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