In Server side:
- A CheckBox is added. If uncheck, no welcome message ("Hello from Android, you are #") will not be sent, such that dataInputStream.readUTF() in client side will be empty.
- After serverSocket.accept(), check available() before call to prevent dataInputStream.readUTF() block the program.
(updated@2014-08-10: after further test, it will lose data sometimes...cannot solve the problem!) - Alternatively, can start another thread to handle DataInputStream.readUTF() and other jobs, such that it will not block the main flow. Reference to the example of "Java/JavaFX Server link to Android Client".
In Client side:
- If "Say hello..." box empty, no dataOutputStream.writeUTF(msgToServer) will be called; such that dataInputStream.readUTF() in server side will be empty.
- If dataInputStream is empty, dataInputStream.readUTF() will block the current thread, but not the UI thread (or called Main Thread). Toast of "MyClientTask ended" will not be shown.
- Another problem is running multi AsyncTask in parallel: Starting with HONEYCOMB, AsyncTask are executed on a single thread to avoid common application errors caused by parallel execution - read Run multi AsyncTask at the same time.
So call myClientTask.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR) if it is running on device higher than HONEYCOMB.
Example code in Server Side:
package com.example.androidserversocket;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.net.InetAddress;
import java.net.NetworkInterface;
import java.net.ServerSocket;
import java.net.Socket;
import java.net.SocketException;
import java.util.Enumeration;
import android.os.Bundle;
import android.app.Activity;
import android.widget.CheckBox;
import android.widget.TextView;
public class MainActivity extends Activity {
TextView info, infoip, msg;
String message = "";
ServerSocket serverSocket;
CheckBox optWelcome;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
info = (TextView) findViewById(R.id.info);
infoip = (TextView) findViewById(R.id.infoip);
msg = (TextView) findViewById(R.id.msg);
optWelcome = (CheckBox)findViewById(R.id.optwelcome);
infoip.setText(getIpAddress());
Thread socketServerThread = new Thread(new SocketServerThread());
socketServerThread.start();
}
@Override
protected void onDestroy() {
super.onDestroy();
if (serverSocket != null) {
try {
serverSocket.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
private class SocketServerThread extends Thread {
static final int SocketServerPORT = 8080;
int count = 0;
@Override
public void run() {
Socket socket = null;
DataInputStream dataInputStream = null;
DataOutputStream dataOutputStream = null;
try {
serverSocket = new ServerSocket(SocketServerPORT);
MainActivity.this.runOnUiThread(new Runnable() {
@Override
public void run() {
info.setText("I'm waiting here: "
+ serverSocket.getLocalPort());
}
});
while (true) {
socket = serverSocket.accept();
dataInputStream = new DataInputStream(
socket.getInputStream());
dataOutputStream = new DataOutputStream(
socket.getOutputStream());
String messageFromClient = "";
//Check available() before readUTF(),
//to prevent program blocked if dataInputStream is empty
if(dataInputStream.available()>0){
messageFromClient = dataInputStream.readUTF();
}
count++;
message += "#" + count + " from " + socket.getInetAddress()
+ ":" + socket.getPort() + "\n"
+ "Msg from client: " + messageFromClient + "\n";
MainActivity.this.runOnUiThread(new Runnable() {
@Override
public void run() {
msg.setText(message);
}
});
if(optWelcome.isChecked()){
String msgReply = "Hello from Android, you are #" + count;
dataOutputStream.writeUTF(msgReply);
}
}
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
final String errMsg = e.toString();
MainActivity.this.runOnUiThread(new Runnable() {
@Override
public void run() {
msg.setText(errMsg);
}
});
} finally {
if (socket != null) {
try {
socket.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
if (dataInputStream != null) {
try {
dataInputStream.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
if (dataOutputStream != null) {
try {
dataOutputStream.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
}
}
private String getIpAddress() {
String ip = "";
try {
Enumeration<NetworkInterface> enumNetworkInterfaces = NetworkInterface
.getNetworkInterfaces();
while (enumNetworkInterfaces.hasMoreElements()) {
NetworkInterface networkInterface = enumNetworkInterfaces
.nextElement();
Enumeration<InetAddress> enumInetAddress = networkInterface
.getInetAddresses();
while (enumInetAddress.hasMoreElements()) {
InetAddress inetAddress = enumInetAddress.nextElement();
if (inetAddress.isSiteLocalAddress()) {
ip += "SiteLocalAddress: "
+ inetAddress.getHostAddress() + "\n";
}
}
}
} catch (SocketException e) {
// TODO Auto-generated catch block
e.printStackTrace();
ip += "Something Wrong! " + e.toString() + "\n";
}
return ip;
}
}
Layout:
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context=".MainActivity" >
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center_horizontal"
android:autoLink="web"
android:text="http://android-er.blogspot.com/"
android:textStyle="bold" />
<TextView
android:id="@+id/info"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
<TextView
android:id="@+id/infoip"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
<CheckBox
android:id="@+id/optwelcome"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:checked="true"
android:text="Send Welcome when connect" />
<ScrollView
android:layout_width="match_parent"
android:layout_height="match_parent" >
<TextView
android:id="@+id/msg"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
</ScrollView>
</LinearLayout>
Download the files.Client side:
package com.example.androidclient;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.net.Socket;
import java.net.UnknownHostException;
import android.os.AsyncTask;
import android.os.Build;
import android.os.Bundle;
import android.annotation.TargetApi;
import android.app.Activity;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;
public class MainActivity extends Activity {
TextView textResponse;
EditText editTextAddress, editTextPort;
Button buttonConnect, buttonClear;
EditText welcomeMsg;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
editTextAddress = (EditText) findViewById(R.id.address);
editTextPort = (EditText) findViewById(R.id.port);
buttonConnect = (Button) findViewById(R.id.connect);
buttonClear = (Button) findViewById(R.id.clear);
textResponse = (TextView) findViewById(R.id.response);
welcomeMsg = (EditText)findViewById(R.id.welcomemsg);
buttonConnect.setOnClickListener(buttonConnectOnClickListener);
buttonClear.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
textResponse.setText("");
}
});
}
OnClickListener buttonConnectOnClickListener = new OnClickListener() {
@TargetApi(Build.VERSION_CODES.HONEYCOMB) @Override
public void onClick(View arg0) {
String tMsg = welcomeMsg.getText().toString();
if(tMsg.equals("")){
tMsg = null;
Toast.makeText(MainActivity.this, "No Welcome Msg sent", Toast.LENGTH_SHORT).show();
}
MyClientTask myClientTask = new MyClientTask(editTextAddress
.getText().toString(), Integer.parseInt(editTextPort
.getText().toString()),
tMsg);
/*
* Handle multi AsyncTask at the same time
* Refer: http://android-er.blogspot.com/2014/04/run-multi-asynctask-as-same-time.html
*/
//myClientTask.execute();
if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB)
myClientTask.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);
else
myClientTask.execute();
}
};
public class MyClientTask extends AsyncTask<Void, Void, Void> {
String dstAddress;
int dstPort;
String response = "";
String msgToServer;
MyClientTask(String addr, int port, String msgTo) {
dstAddress = addr;
dstPort = port;
msgToServer = msgTo;
}
@Override
protected Void doInBackground(Void... arg0) {
Socket socket = null;
DataOutputStream dataOutputStream = null;
DataInputStream dataInputStream = null;
try {
socket = new Socket(dstAddress, dstPort);
dataOutputStream = new DataOutputStream(
socket.getOutputStream());
dataInputStream = new DataInputStream(socket.getInputStream());
if(msgToServer != null){
dataOutputStream.writeUTF(msgToServer);
}
//If dataInputStream is empty,
//readUTF() will block the current thread,
//but not the UI thread (or main thread).
response = dataInputStream.readUTF();
MainActivity.this.runOnUiThread(new Runnable() {
@Override
public void run() {
Toast.makeText(MainActivity.this,
"MyClientTask ended",
Toast.LENGTH_SHORT).show();
}
});
} catch (UnknownHostException e) {
// TODO Auto-generated catch block
e.printStackTrace();
response = "UnknownHostException: " + e.toString();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
response = "IOException: " + e.toString();
} finally {
if (socket != null) {
try {
socket.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
if (dataOutputStream != null) {
try {
dataOutputStream.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
if (dataInputStream != null) {
try {
dataInputStream.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
return null;
}
@Override
protected void onPostExecute(Void result) {
textResponse.setText(response);
super.onPostExecute(result);
}
}
}
Layout:
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
android:orientation="vertical"
tools:context=".MainActivity" >
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center_horizontal"
android:autoLink="web"
android:text="http://android-er.blogspot.com/"
android:textStyle="bold" />
<EditText
android:id="@+id/welcomemsg"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:hint="Say hello to server" />
<EditText
android:id="@+id/address"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:hint="dstAddress" />
<EditText
android:id="@+id/port"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:hint="dstPort" />
<Button
android:id="@+id/connect"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Connect..."/>
<Button
android:id="@+id/clear"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Clear"/>
<TextView
android:id="@+id/response"
android:layout_width="wrap_content"
android:layout_height="wrap_content"/>
</LinearLayout>
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