Android Socket

A Simple TCP client of NIST time server

  • Demo: AndroidTcpDemo-GetNISTTime

    nist_demo

  • Add Internet Permission to AndroidManifest.xml

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

  • Main Activity

    
// This is a simple Client app example to get NIST time
package com.yubao.androidtcpdemo;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.view.View;
import android.widget.TextView;

import com.yubao.androidtcpdemo.databinding.ActivityMainBinding;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.Socket;

public class MainActivity extends AppCompatActivity {

// Used to load the 'androidtcpdemo' library on application startup.
static {
System.loadLibrary("androidtcpdemo");
}

private ActivityMainBinding binding;

private TextView tvTime;
private String serverName = "time.nist.gov";
private int serverPort = 13;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);

binding = ActivityMainBinding.inflate(getLayoutInflater());
setContentView(binding.getRoot());

// Example of a call to a native method
//        TextView tv = binding.sampleText;
//        tv.setText(stringFromJNI());
}

public void onClickGetTime(View view)
{
tvTime = findViewById(R.id.tvTime);
NistTimeClient runable = new NistTimeClient(serverName, serverPort);
new Thread(runable).start();
}

private class NistTimeClient implements Runnable{

private String serverName;
private int serverPort;

public NistTimeClient(String serverName, int serverPort) {
this.serverName = serverName;
this.serverPort = serverPort;
}

@Override
public void run() {
try {
Socket socket = new Socket(serverName, serverPort);
BufferedReader br = new BufferedReader(new InputStreamReader((socket.getInputStream())));
br.readLine();
String recTime = br.readLine().substring(6, 23);
socket.close();

runOnUiThread(new Runnable() {
@Override
public void run() {
tvTime.setText(recTime);
}
});
} catch (IOException e) {
throw new RuntimeException(e);
}

}
}
/**
 * A native method that is implemented by the 'androidtcpdemo' native library,
 * which is packaged with this application.
 */
 public native String stringFromJNI();
 }

  • Design

    <TextView
android:id="@+id/tvTime"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="System Time Here"
android:textSize="34sp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintVertical_bias="0.215" />

<Button
android:id="@+id/btnGetTime"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="34dp"
android:onClick="onClickGetTime"
android:text="Get NIST Time"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.5"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/tvTime" />

Client and Server Example

  • Demo: AndroidTcpClientServer

    Client demo: client_demo

    Server demo: server_demo

  • Add Permission

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

  • Client-end src

    package com.yubao.androidtcpclient;
import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

import com.yubao.androidtcpclient.databinding.ActivityMainBinding;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.Socket;

public class MainActivity extends AppCompatActivity {

// Used to load the 'androidtcpclient' library on application startup.
static {
System.loadLibrary("androidtcpclient");
}

private ActivityMainBinding binding;

// client example
private  TextView tvReceivedData;
private EditText etServerName, etServerPort;
private Button btnClientConnect;
private String serverName;
private int serverPort;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);

binding = ActivityMainBinding.inflate(getLayoutInflater());
setContentView(binding.getRoot());

tvReceivedData = findViewById(R.id.tvReceivedData);
etServerName = findViewById(R.id.etServerName);
etServerPort = findViewById(R.id.etServerPort);
btnClientConnect = findViewById(R.id.btnClientConnect);
}

public void onClictConnect(View view)
{
serverName = etServerName.getText().toString();
serverPort = Integer.valueOf(etServerPort.getText().toString());

new Thread(new Runnable() {
@Override
public void run() {
try {
Socket socket = new Socket(serverName, serverPort);

BufferedReader br_input = new BufferedReader(new InputStreamReader(socket.getInputStream()));
String txtFromServer = br_input.readLine();

runOnUiThread(new Runnable() {
@Override
public void run() {
tvReceivedData.setText(txtFromServer);
}
});
} catch (IOException e) {
throw new RuntimeException(e);
}

}
}).start();
}
public native String stringFromJNI();
}

  • Server-end src

    package com.yubao.androidtcpserver2;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.view.View;
import android.widget.TextView;

import java.io.IOException;
import java.io.PrintStream;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;

public class ServerActivity extends AppCompatActivity {

private TextView tvServerName, tvServerPort, tvStatus;
private String serverIP = "127.0.0.1";
private int serverPort = 8899;

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

tvServerName = findViewById(R.id.tvServerName);
tvServerPort = findViewById(R.id.tvServerPort);
tvStatus = findViewById(R.id.tvStatus);

tvServerName.setText(serverIP );
tvServerPort.setText(String.valueOf(serverPort));
}

private ServerThread serverThread;
public void onCLiickServer(View view)
{
serverThread = new ServerThread();
serverThread.StartServer();
}

public void onClickStopServer(View view){
serverThread.StopServer();
}

class ServerThread extends Thread implements Runnable{
private boolean serverRunning;
private ServerSocket serverSocket;
private int count =0;

public void StartServer()
{
serverRunning = true;
start();
}

@Override
public void run() {
try {
serverSocket = new ServerSocket(serverPort);
runOnUiThread(new Runnable() {
@Override
public void run() {
tvStatus.setText("Waiting for clients");

}
});
while(serverRunning)
{
Socket socket = serverSocket.accept();
count++;
runOnUiThread(new Runnable() {
@Override
public void run() {
tvStatus.setText("Connect to: " + socket.getInetAddress() + " : " +socket.getLocalPort());
}
});
PrintWriter output_server = new PrintWriter(socket.getOutputStream());
output_server.write("Welcome to Server:" + count);
output_server.flush();
socket.close();
}
} catch (IOException e) {
throw new RuntimeException(e);
}
}
public void StopServer(){
serverRunning = false;
new Thread(new Runnable() {
@Override
public void run() {
if (serverSocket != null) {
try {
serverSocket.close();
runOnUiThread(new Runnable() {
@Override
public void run() {
tvStatus.setText("Server Stopped");
}
});
} catch (IOException e) {
throw new RuntimeException(e);
}
}
}
}).start();
}
}// class ServerThread

}
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