The definition of socket in php and a brief introduction to where it is used

This article brings you a brief introduction to the definition of socket in php and usage scenarios. It has certain reference value. Friends in need can refer to it. I hope it will be helpful to you.

Definition of socket && Usage scenarios:

(1) Usage scenarios of socket:
Such as: browser process and web server process communication;
Such as: QQ The process communicates with the friend's QQ process;

(2) Local process communication && Process communication on the network:

(1) Local process communication:

Local There are many ways of inter-process communication (IPC), but they can be summarized into the following three categories:

1. Message passing (pipeline, FIFO, message queue)
2. Synchronization (mutex, condition variable , read-write lock, file and write record lock, semaphore)
3. Shared memory (anonymous and named)

(3) Identify a process:

Can be done locally A process is uniquely identified by process PID, but this does not work in the network.
The "ip address" of the network layer can uniquely identify the host in the network, while the "protocol port" of the transport layer can uniquely identify the application (process) in the host. In this way, the triplet (ip address, protocol, port) can be used to identify the network process.

(2) Process communication on the network:

Applications that use the TCP/IP protocol usually use the application programming interface: UNIX BSD socket.

(3) Definition of socket:

Socket originated from Unix, and one of the basic philosophies of Unix/Linux is that "everything is a file", which can be opened with "open -> read and write" write/read –> operate in "close" mode. My understanding is that Socket is an implementation of this mode. Socket is a special file, and some socket functions are operations on it (read/write IO, open, close)

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