缘起

最近阅读<> (刘金亮, 2021.1)
本系列笔记拟采用golang练习之

案例需求(聊天服务器)

• 用户可以连接到服务器。
• 用户可以设定自己的用户名。
• 用户可以向服务器发送消息，同时服务器也会向其他用户广播该消息。

目标

• 定义通信协议, 包括信令定义, 编解码实现
• 实现聊天客户端(时间有限, 后续实现聊天服务端并测试)

设计

• IMsg: 定义消息接口, 以及相关消息的实现. 为方便任意消息内容的解码, 消息传输时, 采用base64转码
• IMsgDecoder: 定义消息解码器及其实现
• IChatClient: 定义聊天客户端接口
• tChatClient: 聊天客户端, 实现IChatClient接口
• IChatServer: 尚未完成
• tChatServer: 尚未完成

IMsg.go

定义消息接口, 以及相关消息的实现. 为方便任意消息内容的解码, 消息传输时, 采用base64转码

package chat_server
import (
    "encoding/base64"
    "fmt"
)
type IMsg interface {
    Encode() string
}
type NameMsg struct {
    Name string
}
func (me *NameMsg) Encode() string {
    return fmt.Sprintf("NAME %s", base64.StdEncoding.EncodeToString([]byte(me.Name)))
}
type ChatMsg struct {
    Name string
    Words string
}
func (me *ChatMsg) Encode() string {
    return fmt.Sprintf("CHAT %s %s",
        base64.StdEncoding.EncodeToString([]byte(me.Name)),
        base64.StdEncoding.EncodeToString([]byte(me.Words)),
    )
}

IMsgDecoder.go

定义消息解码器及其实现

package chat_server
import (
    "encoding/base64"
    "strings"
)
type IMsgDecoder interface {
    Decode(line string) (bool, IMsg)
}
type tMsgDecoder struct {
}
func (me *tMsgDecoder) Decode(line string) (bool, IMsg) {
    items := strings.Split(line, " ")
    size := len(items)
    if items[0] == "NAME" && size == 2 {
        name, err := base64.StdEncoding.DecodeString(items[1])
        if err != nil {
            return false, nil
        }
        return true, &NameMsg{
            Name: string(name),
        }
    }
    if items[0] == "CHAT" && size == 3 {
        name, err := base64.StdEncoding.DecodeString(items[1])
        if err != nil {
            return false, nil
        }
        words, err := base64.StdEncoding.DecodeString(items[2])
        if err != nil {
            return false, nil
        }
        return true, &ChatMsg{
            Name: string(name),
            Words: string(words),
        }
    }
    return false, nil
}
var MsgDecoder = &tMsgDecoder{}

IChatClient.go

定义聊天客户端接口

package chat_server
type IChatClient interface {
    Dial(address string) error
    Send(msg IMsg)
    RecvHandler(handler RecvFunc)
    Close()
}
type RecvFunc func(msg IMsg)

tChatClient.go

聊天客户端, 实现IChatClient接口

package chat_server
import (
    "bufio"
    "net"
    "sync/atomic"
)
type tChatClient struct {
    conn net.Conn
    closeFlag int32
    closeChan chan bool
    sendChan chan IMsg
    name string
    sendLogs []IMsg
    recvLogs []IMsg
    recvHandler RecvFunc
}
func DialChatClient(address string) (error, IChatClient) {
    it := &tChatClient{
        conn: nil,
        closeFlag: 0,
        closeChan: make(chan bool),
        sendChan: make(chan IMsg),
        name: "anonymous",
        sendLogs: []IMsg{},
        recvLogs: []IMsg{},
    }
    e := it.Dial(address)
    if e != nil {
        return e, nil
    }
    return nil, it
}
func (me *tChatClient) Dial(address string) error {
    c, e := net.Dial("tcp", address)
    if e != nil {
        return e
    }
    me.conn = c
    go me.beginWrite()
    go me.beginRead()
    return nil
}
func (me *tChatClient) isClosed() bool {
    return me.closeFlag != 0
}
func (me *tChatClient) isNotClosed() bool {
    return !me.isClosed()
}
func (me *tChatClient) Send(msg IMsg) {
    if me.isNotClosed() {
        me.sendChan <- msg
    }
}
func (me *tChatClient) RecvHandler(handler RecvFunc) {
    if me.isNotClosed() {
        me.recvHandler = handler
    }
}
func (me *tChatClient) Close() {
    if me.isNotClosed() {
        me.closeConn()
    }
}
func (me *tChatClient) beginWrite() {
    writer := bufio.NewWriter(me.conn)
    newline := '\n'
    for {
        select {
        case <- me.closeChan:
            _ = me.conn.Close()
            me.closeFlag = 2
            return
        case msg := <- me.sendChan:
            _,e := writer.WriteString(msg.Encode())
            if e != nil {
                me.closeConn()
            } else {
                _,e = writer.WriteRune(newline)
                if e != nil {
                    me.closeConn()
                }
            }
        }
    }
}
func (me *tChatClient) beginRead() {
    reader := bufio.NewReader(me.conn)
    for me.isNotClosed() {
        line, _, err := reader.ReadLine()
        if err != nil {
            break
        }
        ok, msg := MsgBuilder.Build(string(line))
        if ok {
            fn := me.recvHandler
            if fn != nil {
                fn(msg)
            }
        }
    }
}
func (me *tChatClient) closeConn() {
    if atomic.CompareAndSwapInt32(&me.closeFlag, 0, 1) {
        me.closeChan <- true
    }
}

(未完待续)