golang tcp library implementation

Go language is an increasingly popular programming language. It has become the focus of everyone's attention with its efficient, concise coding style, natural concurrency and concurrent programming model. For TCP protocol communication, Go language provides some built-in libraries to help us implement TCP communication, such as net, net/http, etc.

This article will explain from the implementation level how to use the Go language socket library to implement TCP communication.

Introduction to TCP protocol

TCP is the Transmission Control Protocol, which is a connection-oriented, reliable, byte stream-based transmission protocol. In the TCP protocol, three handshakes are required before data is sent to ensure the correct transmission of data. During the data transmission process, TCP also provides some data verification, retransmission and other mechanisms to ensure the reliability of the data. Therefore, TCP is also called a reliable transport protocol.

Overview of the socket library of Go language

Go language provides a native socket library, which mainly includes three packages: net, net/http, and net/rpc. Among them, the net package provides the most basic network communication operation interface, including IP address, TCP/UDP protocol, etc.; the net/http package provides a network operation interface related to the HTTP protocol; net/rpc is a remote procedure call framework.

In the net package, there are two main types: Conn and Listener. Among them, Conn represents a connection-oriented communication. Both the client and the server can have a Conn object. Conn can realize communication between two computers; Listener represents a network port listener, which can be used to monitor and process the client's Link request, return Conn object to achieve communication.

Use the socket library to implement TCP communication

After understanding the TCP protocol and the socket library of the Go language, we can start to use the socket library of the Go language to implement TCP communication. The following uses a simple example to explain how to use the socket library to implement TCP communication.

Server side

Let’s first take a look at how to implement a simple TCP server-side program. The sample code is as follows:

package main

import (
    "fmt"
    "net"
)

func main() {
    listener, err := net.Listen("tcp", "127.0.0.1:8888")
    if err != nil {
        fmt.Println("Error: ", err)
        return
    }

    for {
        conn, err := listener.Accept()
        if err != nil {
            fmt.Println("Error: ", err)
            continue
        }
        go handleConn(conn)
    }
}

func handleConn(conn net.Conn) {
    defer conn.Close()

    buf := make([]byte, 1024)
    for {
        n, err := conn.Read(buf)
        if err != nil {
            fmt.Println("Error: ", err)
            return
        }

        fmt.Println("Receive: ", string(buf[:n]))

        _, err = conn.Write(buf[:n])
        if err != nil {
            fmt.Println("Error: ", err)
            return
        }
    }
}

In this sample program, we use the Listen function of the net package to listen to the local 8888 port, and use a for loop in the main function to continuously wait for the client's link request. Once a connection request is obtained, a new coroutine is created to handle the connection request, thereby enabling concurrent processing of multiple clients.

In the handleConn function, we first use defer to ensure that the current link will be closed after the program is executed, then use the Read function to read data from the client, and use the Write function to send data to the client, achieving a simple Echo function.

Client

Next, let’s take a look at how to implement a simple TCP client program. The sample code is as follows:

package main

import (
    "fmt"
    "net"
)

func main() {
    conn, err := net.Dial("tcp", "127.0.0.1:8888")
    if err != nil {
        fmt.Println("Error: ", err)
        return
    }
    defer conn.Close()

    _, err = conn.Write([]byte("Hello World!"))
    if err != nil {
        fmt.Println("Error: ", err)
        return
    }

    buf := make([]byte, 1024)
    n, err := conn.Read(buf)
    if err != nil {
        fmt.Println("Error: ", err)
        return
    }

    fmt.Println("Receive: ", string(buf[:n]))
}

In this sample program, we use the Dial function of the net package to connect to the server, send a piece of data to the server, and use the Read function to read the data returned by the server. If no errors occur, print out the data returned by the server.

Summary

Through the explanation of this article, we have learned about the basic knowledge of the TCP protocol and the implementation of the socket library in the Go language. At the same time, we also demonstrated how to use the socket library of Go language to implement TCP communication through a simple sample program. In actual development, different application scenarios may require the use of TCP communication, and mastering the ability to use the socket library will become one of the essential skills for programmers.

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