What is socket in php? Detailed explanation of socket examples

What is Socket?

Socket is an intermediate software abstraction layer that communicates between the application layer and the TCP/IP protocol suite. It is a set of interfaces. In the design mode, Socket is actually a facade mode, which hides the complex TCP/IP protocol family behind the Socket interface. For users, a set of simple interfaces is all, allowing Socket to organize data to meet the specified requirements. protocol. It has been rare to see many people using PHP’s socket module to do some things. Probably everyone places it within the scope of scripting languages, but in fact, PHP’s socket module can do many things, including doing ftplist , http post submission, smtp submission, group package and interaction of special messages (such as smpp protocol), whois query. These are some of the more common queries. Especially what PHP's socket extension library can do is not much worse than C.

Socket Basics

php uses Berkley's socket library to create its connections. You can know that socket is just a data structure. Use this socket data structure to start a session between the client and the server. This server is always listening and preparing to generate a new session. When a client connects to the server, it opens a port on which the server is listening for a session. At this time, the server accepts the client's connection request and then performs a cycle. Now the client can send information to the server, and the server can send information to the client.
To generate a Socket, three variables are required: A protocol, a socket type and a public protocol type. There are three protocols to choose from when generating a socket. Continue reading below to get detailed protocol content. Defining a public protocol type is an essential element of connection. Let's take a look at these common protocol types.

1. Protocol

##Name/Constant DescriptionAF_INETThis is the protocol most used to generate sockets, using TCP or UDP for transmission, and used in IPv4 addresses AF_INET6 Similar to the above, but used for IPv6 addressesAF_UNIX Local protocol, used on Unix and Linux systems, it Rarely used, usually used when the client and server are on the same machine

2. Socket type

#Name/Constant DescriptionSOCK_STREAMThis protocol is a sequential, reliable, data-integrated byte stream-based connection. This is the most commonly used socket type. This socket uses TCP for transmission. SOCK_DGRAMThis protocol is a connectionless, fixed-length transfer call. This protocol is unreliable and uses UDP for its connections. SOCK_SEQPACKETThis protocol is a two-line, reliable connection that sends fixed-length data packets for transmission. This packet must be accepted completely before it can be read. SOCK_RAWThis socket type provides single network access. This socket type uses the ICMP public protocol. (ping and traceroute use this protocol) SOCK_RDMThis type is rarely used and is not implemented on most operating systems. It is provided for data Used by the link layer, the order of data packets is not guaranteed3. Public protocol

Name/Constant DescriptionICMPInternet Control Message Protocol, mainly used on gateways and hosts, used To check network conditions and report error messagesUDPUser Datagram Protocol, it is a connectionless, unreliable transmission protocolTCPTransmission Control Protocol, this is the most commonly used reliable public protocol. It can ensure that the data packet can reach the recipient. If an error occurs during the transmission, then it will Resend the error packet.

Knowing the three elements that generate a socket, then we use the socket_create() function in php to generate a socket. The socket_create() function requires three parameters: a protocol, a socket type, and a public protocol. The socket_create() function returns a resource type containing the socket if it runs successfully. If it fails, it returns false.

Resourece socket_create(int protocol, int socketType, int commonProtocol);

php provides several functions for manipulating sockets, which can bind the socket to an IP, monitor the communication of a socket, and accept a socket; now let's look at an example to understand how the function is generated , accept and listen to a socket.

The code is as follows:

<?php
$commonProtocol = getprotobyname("tcp");
$socket = socket_create(AF_INET, SOCK_STREAM,$commonProtocol);
socket_bind($socket,&#39;localhost&#39;,1337);
socket_listen($socket);
?>

Instructions: The above example generates your own server.

The first line of the example uses the public protocol name to obtain a protocol type. The TCP public protocol is used here. If you want to use UDP or ICMP protocol, then you should change the parameters of the getprotobyname() function to "udp" or "icmp". An alternative is to not use the getprotobyname() function but specify SOL_TCP or SOL_UDP in the socket_create() function.
The second line of the example generates a socket and returns an instance of the socket resource. After you have an instance of the socket resource, you must bind the socket to an IP address and a port.
The third line here binds the socket to the local computer (127.0.0.1) and binds the socket to your 1337 port. Then you need to listen for all incoming socket connections. After the fourth line, you need to understand all socket functions and their usage. The socket function will be explained in detail in later chapters.

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