接收

@SuppressLint("StaticFieldLeak")
    AsyncTask<Void,String,Void> asyncTask_read = new AsyncTask<Void, String, Void>() {
        @Override
        protected Void doInBackground(Void... voids) {
            try {

                InetAddress serverIp = InetAddress.getByName("你的實體IP");
                socket_chat = new Socket(serverIp,12345);


                // 第一次開啟聊天室
                Intent intent_server_change = new Intent("socket_server_change");
                intent_server_change.putExtra("socket_server_change", "open");
                sendBroadcast(intent_server_change);

                // 推到 Progress
                br_chat = new BufferedReader(new InputStreamReader(socket_chat.getInputStream()));
                String line ;
                while((line = br_chat.readLine()) != null) {
                    publishProgress(line);
                }
            }catch (Exception k ){
                socket_chat = null;
                Intent intent_server_change = new Intent("socket_server_change");
                intent_server_change.putExtra("socket_server_change","close");
                sendBroadcast(intent_server_change);
                k.printStackTrace();
            }
            return null;

        };

        @Override
        protected void onProgressUpdate(String... values) {

            if(!values[0].substring(0,2).equals("$$")) {

                // 推送訊息
                Intent intent_send = new Intent("chat");
                intent_send.putExtra("chat",values[0]+"\n");
                sendBroadcast(intent_send);
                
                // 暫存訊息，回聊天室畫面時可以傳送
                // 也可以不要殺死聊天室的 Activity 就好
                if (Chat_str.size() >= 5) {
                    Chat_str.remove(0);
                }
                // 聊天室固定加入訊息不暫存
                if (!(values[0].equals("**已成功連線，歡迎加入聊天室**"))) {
                    Chat_str.add(values[0] + "\n");
                }
            }else {
                   
                // 跑馬燈公告
                Intent intent_server_change = new Intent("marquee_send");
                intent_server_change.putExtra("marquee_send",values[0].substring(2));
                sendBroadcast(intent_server_change);
            }
            super.onProgressUpdate(values);
        }
    };

    asyncTask_read.execute();

送出訊息給 Server

if(socket != null && socket.isConnected() ) {
    final Thread thread = new Thread(new Runnable() {
        @Override
        public void run() {
            try {
                BufferedWriter bw ;
                bw = new BufferedWriter(new OutputStreamWriter(socket.getOutputStream()));
                bw.write(send_message);
                bw.flush();
                
                // 清除 Edittext 
                Chatedit_clean.sendEmptyMessage(0);
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    });
    thread.start();
}else {
    Chat.append("聊天伺服器目前關閉中\n");
    scrollView.fullScroll(ScrollView.FOCUS_DOWN);
}

這邊我是將接收訊息寫在 Service 裡面，BindService 溝通取得裡面的 Socket 物件