Commonly used functions in php socket programming and the implementation of simple c/s interaction

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Socket Introduction

Official explanation of Socket:
The most commonly used solution in network programming is the Client/Server (client/server) model. In this scenario the client application requests services from the server program. A service program usually listens for requests for the service at a well-known address. That is to say, the service process remains dormant until a client makes a connection request to the service's address. At this moment, the service program is "awakened" and provides services to the client - reacting appropriately to the client's request. In order to facilitate network programming of this Client/Server model, in the early 1990s, Microsoft and several other companies jointly developed a set of network programming interfaces under WINDOWS, namely the Windows Sockets specification. It is not a network protocol, but a network programming interface. A set of open network programming interfaces under Windows that support multiple protocols. Now Winsock has basically become protocol-independent. You can use Winsock to call functions of multiple protocols, but the TCP/IP protocol is more commonly used. Socket actually provides a communication port in the computer through which it can communicate with any computer that has a Socket interface. The application transmits on the network, and the information received is realized through this Socket interface

We can simply understand Socket as a pipe that can connect different computer applications on the network, and transfer a bunch of data from If the A end of the pipe is thrown in, it will come out from the B end of the pipe (it can also come out from the C, D, E, F... ends).

Note: We will use different words to modify socket in different contexts. You only need to have a concept of it, because socket itself has no real meaning. Entity

Socket function introduction

Socket communication will proceed through several stages: Socket creation, Socket binding, Socket monitoring, Socket sending and receiving, and Socket closing. We list them below. Several common functions that are most commonly used and essential in PHP network programming are further explained.

socket_create

TODO: Create a new socket resource
Function prototype: resource socket_create (int $domain, int $type, int $protocol)
It contains three parameters, as follows:

• domain: AF_INET, AF_INET6, AF_UNIX, the definition of AF is address family, address Family means, we commonly use ipv4, ipv6

• type: SOCK_STREAM, SOCK_DGRAM, etc. The most commonly used one is SOCK_STREAM, a SOCKET type based on byte stream, It is also the type used by TCP protocol

• protocol: SOL_TCP, SOL_UDP This is the specific transmission protocol used. Generally, we choose TCP for reliable transmission, and we generally choose UDP protocol for game data transmission

socket_bind

TODO: Bind the created socket resource to a specific ip address and port
Function prototype: bool socket_bind (resource $socket, string $ address [, int $port = 0 ] )

It contains three parameters, as follows:

• socket: Use socket_create The created socket resource can be considered as the id corresponding to the socket

• address: ip address

• port: listening port number, WEB server default Port 80

socket_listen

TODO: Monitor the sending and receiving operations of socket resources at a specific address
Function prototype: bool socket_listen (resource $socket [ , int $backlog = 0 ] )

It contains two parameters, as follows:

• socket: Created using socket_create Socket resource

• backlog: The maximum length of the connection queue waiting to be processed

socket_accept

TODO: After listening, receive a The upcoming new connection, if the connection is successfully established, will return a new socket handle (you can understand it as a child process, usually the parent process is used to receive new connections, and the child process is responsible for specific communication)
Function prototype: resource socket_accept ( resource $socket )

• socket: socket resource created using socket_create

socket_write

TODO: Send the specified data to the corresponding socket pipe
Function prototype: int socket_write (resource $socket, string $buffer [, int $length])

• socket: socket resource created using socket_create

• buffer: written to socket resource Data in

• length: Controls the length of buffer written to the socket resource, if the length is greater than buffer’s capacity, take the capacity of buffer

socket_read

TODO: Get the transmitted data
Function prototype: int socket_read (resource $socket, int $length)

• socket: The socket resource created using socket_create

• length: buffer# in the socket resource ##The length

socket_close

TODO: Close the socket resource

Function prototype:
void socket_close (resource $socket)

• socket: The resources generated by

  socket_accept or socket_create cannot be used to close stream resources

stream_socket_server

Since the process of creating a SOCKET is always socket, bind, and listen, PHP provides a very convenient function to create, bind ports, and listen to ports at once

Function prototype:

resource stream_socket_server ( string $local_socket [, int &$errno [, string &$errstr [, int $flags = STREAM_SERVER_BIND | STREAM_SERVER_LISTEN [, resource $context ]]]] )

• local_socket: protocol name://address:port number

• errno: error code

• errstr: Error message

• #flags: Only use part of the function

• context: Resource stream created using the

  stream_context_create function Context

socket implements C/S interaction

Based on the above functions, we can easily build a socket communication program (here I hope Readers can create a separate directory such as

socket (because we will create many files later). We first edit a server program server.php, as follows:

Then Edit a client program

client.php as follows:

Then we open the terminal (command line) and enter the file directory to execute in sequence:

php server.php
php client.php

The running effect is as follows:

NoteWhen the server is listening, the process is suspended and no other operations can be performed. You may need to start another terminal to execute the client Terminal program

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