Copy Coding

//client 접속 대기

Socket client = serverSocket.accept();

//client data 수신

BufferedReader in = new BufferedReader(new InputStreamReader(client.getInputStream()));

String str = in.readLine();

//client에 다시 전송

PrintWriter out = new PrintWriter(new BufferedWriter(new OutputStreamWriter(client.getOutputStream())), true);

out.println("Server Received : '" + str + "'");

//소켓 생성
InetAddress serverAddr = InetAddress.getByName(ip);
 socket =  new Socket(serverAddr,port);
//입력 메시지
String sndMsg = et.getText().toString();
//데이터 전송
PrintWriter out = new PrintWriter(new BufferedWriter(new OutputStreamWriter(socket.getOutputStream())),true);
out.println(sndMsg);
//데이터 수신
BufferedReader input = new BufferedReader(new InputStreamReader(socket.getInputStream()));
String read = input.readLine();

package egovframework.admin.chart.web;

import java.io.BufferedReader;

import java.io.BufferedWriter;

import java.io.InputStreamReader;

import java.io.ObjectOutputStream;

import java.io.OutputStreamWriter;

import java.io.PrintWriter;

import java.net.ServerSocket;

import java.net.Socket;

public class TCPServer implements Runnable {

             public static final int ServerPort = 9999;

//    public static final String ServerIP = "192.168.0.6";

             @Override

             public void run() {

                           try {

            System.out.println("Connecting...");

            ServerSocket serverSocket = new ServerSocket(ServerPort);

            while (true) {

                     //client 접속 대기

                Socket client = serverSocket.accept();

                System.out.println("Receiving...");

                try {

                   //client data 수신

                    BufferedReader in = new BufferedReader(new InputStreamReader(client.getInputStream()));

                    String str = in.readLine();

                    System.out.println("Received: '" + str + "'");

                    //client에 다시 전송

                    PrintWriter out = new PrintWriter(new BufferedWriter(new OutputStreamWriter(client.getOutputStream())), true);

                    out.println("Server Received : '" + str + "'");

                } catch (Exception e) {

                    System.out.println("Error");

                    e.printStackTrace();

                } finally {

                    client.close();

                    System.out.println("Done.");

                }

            }

        } catch (Exception e) {

            System.out.println("S: Error");

            e.printStackTrace();

        }

             }

             public static void main(String[] args) {

        Thread ServerThread = new Thread(new TCPServer());

        ServerThread.start();

     }

}

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <TextView
        android:id="@+id/TextView01"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content" />

    <EditText
        android:id="@+id/EditText01"
        android:layout_width="289dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="92dp"
        app:layout_constraintStart_toStartOf="@+id/Button01"
        tools:layout_editor_absoluteY="0dp" />

    <Button
        android:id="@+id/Button01"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Send" />

    <Button
        android:id="@+id/button02"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginEnd="16dp"
        android:layout_marginTop="456dp"
        android:text="Connect"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <TextView
        android:id="@+id/chatTV"
        android:layout_width="fill_parent"
        android:layout_height="381dp"
        android:layout_marginTop="64dp"
        app:layout_constraintTop_toTopOf="@+id/TextView01"
        tools:layout_editor_absoluteX="0dp" />
</android.support.constraint.ConstraintLayout>

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.tcpclient">

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

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

package com.example.tcpclient;

import android.os.Handler;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.net.InetAddress;
import java.net.InetSocketAddress;
import java.net.Socket;
import java.net.UnknownHostException;


public class MainActivity extends AppCompatActivity {

    private Handler mHandler;
    Socket socket;
    private String ip = "192.168.0.6"; // IP 주소
    private int port = 9999; // PORT번호
    EditText et;
    TextView msgTV;

    @Override
    protected void onStop() {
        super.onStop();
        try {
            socket.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        mHandler = new Handler();

        et = (EditText) findViewById(R.id.EditText01);
        Button btn = (Button) findViewById(R.id.Button01);
        Button btnCon = (Button)findViewById(R.id.button02);
        final TextView tv = (TextView) findViewById(R.id.TextView01);
        msgTV = (TextView)findViewById(R.id.chatTV);

        btn.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                if (et.getText().toString() != null || !et.getText().toString().equals("")) {
                    ConnectThread th =new ConnectThread();
                    th.start();
                }
            }
        });
    }

    class ConnectThread extends Thread{
        public void run(){
            try{
                //소켓 생성
                InetAddress serverAddr = InetAddress.getByName(ip);
                 socket =  new Socket(serverAddr,port);
                //입력 메시지
                String sndMsg = et.getText().toString();
                Log.d("=============", sndMsg);
                //데이터 전송
                PrintWriter out = new PrintWriter(new BufferedWriter(new OutputStreamWriter(socket.getOutputStream())),true);
                out.println(sndMsg);
                //데이터 수신
                BufferedReader input = new BufferedReader(new InputStreamReader(socket.getInputStream()));
                String read = input.readLine();
                //화면 출력
                mHandler.post(new msgUpdate(read));
                Log.d("=============", read);
                socket.close();
            }catch(Exception e){
                e.printStackTrace();
            }
        }
    }
    // 받은 메시지 출력
    class msgUpdate implements Runnable {
        private String msg;
        public msgUpdate(String str) {
            this.msg = str;
        }
        public void run() {
            msgTV.setText(msgTV.getText().toString() + msg + "\n");
        }
    };
}