服務端保持等待來自客戶端的連線和接收來自客戶端的訊息

服務端：

class MainActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        Thread{
            kotlin.run {
                var serverSocket: ServerSocket
 
? = null
                try {
                    serverSocket = ServerSocket(8866)
                    while (true){
                        println("等待來自客戶端的連結...")
                        var socket: Socket = serverSocket.accept()
                        println("客戶端已連結...")
                        var bufferIn 
 
= BufferedReader(InputStreamReader(socket.getInputStream()))
                        var recvMsg = bufferIn!!.readLine() + System.getProperty("line.separator")
                        println("接收到的資訊$recvMsg")
                        //給客戶端回一條資訊
                        var bufferedout:BufferedWriter= BufferedWriter(OutputStreamWriter(socket.getOutputStream()))
                        var sendMsg
 
="我已收到你發的資訊" + System.getProperty("line.separator")
                        bufferedout.write(sendMsg)
                        bufferedout.flush()
                    }
                }catch (e:InterruptedIOException) {
                    // 超時錯誤
                    e.printStackTrace();
                    // IO 異常
                } catch (e:IOException) {
                    // 列印錯誤
                    e.printStackTrace();
                } finally {
                    // 判定是否初始化 ServerSocket 物件，如果初始化則關閉 serverSocket
                    if (serverSocket != null) {
                        try {
                            serverSocket.close();
                        } catch (e:IOException) {
                            e.printStackTrace();
                        }
                    }
                }
            }
        }.start()
    }
}

客戶端

class MainActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        Thread{
            kotlin.run {
                try{
                    var socket:Socket= Socket("10.0.2.15",8866)
                    var buffIn:BufferedReader=BufferedReader(InputStreamReader(socket.getInputStream()))
                    var buffOut:BufferedWriter= BufferedWriter(OutputStreamWriter(socket.getOutputStream()))
                    var outMsg:String="Tcp connection to 8866"+System.getProperty("line.separator")
                    buffOut.write(outMsg)
                    buffOut.flush()
                    var inMsg=buffIn.readLine()+System.getProperty("line.separator")
                    //Log.i("TCPClient", "received:$inMsg")
                    println("接受到的訊息:$inMsg")
                    socket.close()
                }catch (e: UnknownHostException){
                    e.printStackTrace()
                }catch (e:IOException){
                    e.printStackTrace()
                }
            }
        }.start()
    }
}

在服務端和客戶端新增網路許可權

 <uses-permission android:name="android.permission.INTERNET"/>

執行：

執行服務端

執行客戶端

服務端顯示

結束客戶端，重新執行客戶端，服務端顯示

這樣大概就能實現簡單的聊天了吧~