【Go基础】搭建TCP服务端、客户端

- 日理万妓 2022-09-03 14:25 274阅读 0赞

# 搭建TCP服务端、客户端 #

*  搭建TCP服务端、客户端
    
     *  TCP基础介绍
     *  服务端Listen函数
     *  客户端Dial函数
     *  搭建TCP服务端、客户端示例
     *  相关资料

--------------------

## TCP基础介绍 ##

TCP协议（`Transmission Control Protocol`）是一个安全、可靠、稳定、有序的数据报传输协议。如果说网络层（通过`ip地址`）解决了主机识别的问题，那么TCP协议则是（通过`端口号`）解决了如何识别主机上唯一一个进程的问题。

TCP还定义数据报的请求序号和确认序号，以确保消息的准确有序。

TCP通过三次握手、四次挥手,保障传输的安全性。  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2p1c3RyeV9kZW5n_size_16_color_FFFFFF_t_70]

## 服务端Listen函数 ##

> Listen函数：
> 
> `func Listen(network, address string) (Listener, error)`
> 
>  *  `network`：网络类型，可以填写`tcp`或`udp`。
>  *  `address`：设定服务器地址，格式为`[ip]:端口`, `ip`可以省略，缺省默认值为`0.0.0.0`
>  *  `error`：返回nil代表无错误，否者存在错误
>  *  `Listener`：监听者对象，用于后续的步骤处理
>     
>      *  `Listener`：
>     
>         // A Listener is a generic network listener for stream-oriented protocols.
>         //
>         // Multiple goroutines may invoke methods on a Listener simultaneously.
>         type Listener interface { 
>         	// Accept waits for and returns the next connection to the listener.
>         	Accept() (Conn, error)
>         
>         	// Close closes the listener.
>         	// Any blocked Accept operations will be unblocked and return errors.
>         	Close() error
>         
>         	// Addr returns the listener's network address.
>         	Addr() Addr
>         }
>     
>      *  `Listener#Accept`返回的`Conn`：
>     
>         // Conn is a generic stream-oriented network connection.
>         //
>         // Multiple goroutines may invoke methods on a Conn simultaneously.
>         type Conn interface { 
>         	// Read reads data from the connection.
>         	// Read can be made to time out and return an error after a fixed
>         	// time limit; see SetDeadline and SetReadDeadline.
>         	Read(b []byte) (n int, err error)
>         
>         	// Write writes data to the connection.
>         	// Write can be made to time out and return an error after a fixed
>         	// time limit; see SetDeadline and SetWriteDeadline.
>         	Write(b []byte) (n int, err error)
>         
>         	// Close closes the connection.
>         	// Any blocked Read or Write operations will be unblocked and return errors.
>         	Close() error
>         
>         	// LocalAddr returns the local network address.
>         	LocalAddr() Addr
>         
>         	// RemoteAddr returns the remote network address.
>         	RemoteAddr() Addr
>         
>         	// SetDeadline sets the read and write deadlines associated
>         	// with the connection. It is equivalent to calling both
>         	// SetReadDeadline and SetWriteDeadline.
>         	//
>         	// A deadline is an absolute time after which I/O operations
>         	// fail instead of blocking. The deadline applies to all future
>         	// and pending I/O, not just the immediately following call to
>         	// Read or Write. After a deadline has been exceeded, the
>         	// connection can be refreshed by setting a deadline in the future.
>         	//
>         	// If the deadline is exceeded a call to Read or Write or to other
>         	// I/O methods will return an error that wraps os.ErrDeadlineExceeded.
>         	// This can be tested using errors.Is(err, os.ErrDeadlineExceeded).
>         	// The error's Timeout method will return true, but note that there
>         	// are other possible errors for which the Timeout method will
>         	// return true even if the deadline has not been exceeded.
>         	//
>         	// An idle timeout can be implemented by repeatedly extending
>         	// the deadline after successful Read or Write calls.
>         	//
>         	// A zero value for t means I/O operations will not time out.
>         	SetDeadline(t time.Time) error
>         
>         	// SetReadDeadline sets the deadline for future Read calls
>         	// and any currently-blocked Read call.
>         	// A zero value for t means Read will not time out.
>         	SetReadDeadline(t time.Time) error
>         
>         	// SetWriteDeadline sets the deadline for future Write calls
>         	// and any currently-blocked Write call.
>         	// Even if write times out, it may return n > 0, indicating that
>         	// some of the data was successfully written.
>         	// A zero value for t means Write will not time out.
>         	SetWriteDeadline(t time.Time) error
>         }

## 客户端Dial函数 ##

> Dial函数：
> 
> `func Dial(network, address string) (Conn, error)`
> 
>  *  `network`：网络类型，可以填写`tcp`或`udp`。
>  *  `address`：设定服务器地址，格式为`[ip]:端口`, `ip`可以省略，缺省默认值为`0.0.0.0`
>  *  `error`：返回nil代表无错误，否者存在错误
>  *  `Conn`：和服务端通信的连接对象。
>     
>     注：`Conn`对象的具体信息上文已经给出，这里不再赘述。

## 搭建TCP服务端、客户端示例 ##

*  TCP服务端

import (
    	"fmt"
    	"log"
    	"net"
    )
    
    func main() { 
    	// 1. 绑定ip和端口，设置监听
    	listener, err := net.Listen("tcp", "localhost:8888")
    	if err != nil { 
    		log.Panic("Failed to Listen", err)
    	}
    	// 延迟关闭，释放资源
    	defer listener.Close()
    
    	// 2. 循环等待新连接
    	for { 
    		// 从连接列表获取新连接
    		conn, err := listener.Accept()
    		if err != nil { 
    			fmt.Println("Failed to Accept", err)
    		}
    		// 3. 与新连接通信(为了不同步阻塞，这里开启异步协程进行函数调用)
    		go handle_conn(conn)
    	}
    }
    
    /** * 处理连接 */
    func handle_conn(conn net.Conn) { 
    	defer conn.Close()
    	fmt.Println("New connection ", conn.RemoteAddr())
    	// 通信
    	buf := make([]byte, 256)
    	for { 
    		// 从网络中读
    		readBytesCount, err := conn.Read(buf)
    		if err != nil { 
    			fmt.Println("Failed to read", err)
    			break
    		}
    		// 提示：buf[:n]的效果为：读取buf[总长度-n]至buf[n]处的字节
    		fmt.Println("服务端收到数据：\t", string(buf[:readBytesCount]))
    
    		// 写回网络 -- 收到什么就写回什么，即：回射服务器
    		writeByteCount, err := conn.Write(buf[:readBytesCount])
    		if err != nil { 
    			fmt.Println("Failed to write", err)
    			break
    		}
    		fmt.Printf("write success %d bytes\n", writeByteCount)
    	}
    }

*  TCP客户端

import (
    	"fmt"
    	"net"
    	"os"
    )
    
    func main() { 
    	// 1. 建立连接
    	conn, err := net.Dial("tcp", "localhost:8888")
    	if err != nil { 
    		fmt.Println("Failed to Dial")
    		return
    	}
    	// 延迟关闭，释放资源
    	defer conn.Close()
    
    	// 2. 与服务端通信
    	buf := make([]byte, 256)
    	for { 
    		// 2.1 从控制台读取输入
    		readBytesCount, _ := os.Stdin.Read(buf)
    		// 2.2 写到网络(即：发送请求)
    		conn.Write(buf[:readBytesCount])
    		// 2.3 读网络(即：获取响应)
    		readBytesCount, _ = conn.Read(buf)
    		// 2.4 输出到控制台
    		// 提示：buf[:n]的效果为：读取buf[总长度-n]至buf[n]处的字节
    		os.Stdout.Write(buf[:readBytesCount])
    	}
    }

*  通信测试

> 先启动server端，再启动client端，然后在client端的控制台进行任意输入触发进行TCP请求，
> 
> 1.  在server端控制台，可看到来自client的请求信息  
>     ![xx][]
> 2.  在client端控制台，可看到来自server端的响应信息  
>     ![在这里插入图片描述][2ee2049bae2249d18204c8810e35eef6.png]

--------------------

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[xx]: /images/20220829/c0abf81aad8d44ddb27e7e772de6c1ed.png
[2ee2049bae2249d18204c8810e35eef6.png]: /images/20220829/8110b01e247243bcbae4906770e6cbff.png
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