Android USB connection to PC
Back a while ago I wrote a post regarding USB cable communication between an Android smartphone and the host machine. I promised some code back then, but forgot to put it. Here is some sample code now.
1a. To enable this to work, the host computer must do what is called port forwarding. The Android debug bridge has this all figured out, you just need to execute the command. What it does, if it executes successfully, is forward all communication targeting localhost on the specified port to the smartphone at the specified port. So, after this, to get a connection, all you have to do is connect to “localhost” on that port you wrote there.
C:\android-sdk-windows\tools\adb.exe forward tcp:38300 tcp:38300
Note: the ports do not have to be the same, I just used the same port for convenience; also you can use any port that will work, the numbers are not special in anyway.
1b. You can also run this directly from your program. Here’s an example of how to do it:
/**
* Runs the android debug bridge command of forwarding the ports
*
*/
private void execAdb() {
// run the adb bridge
try {
Process p=Runtime.getRuntime().exec("C:\\android-sdk-windows\\tools\\adb.exe forward tcp:38300 tcp:38300");
Scanner sc = new Scanner(p.getErrorStream());
if (sc.hasNext()) {
while (sc.hasNext()) System.out.println(sc.next());
Print.fatalError("Cannot start the Android debug bridge");
}
} catch (Exception e) {
Print.fatalError(e.toString());
}
}
2. The server socket needs to be on the smartphone. Not exactly sure why that is, but I couldn’t get this thing to work when it was on the host. My guess is that it has something to do with the way port forwarding works.
Also, it’s usually a good idea to put this part on a separate thread so it doesn’t lock up your UI. The Android tutorial talks more about that in UI design so I won’t.
The sample code that follows does two things. First, it creates a server socket to listen for connections. Second, it actually waits for a connection to be established. It then announces this and goes on to the next class. If in 10 seconds no connection occurs, it times out and stops trying.
NOTE: the following code will not run by itself, because the UI is in an XML file that’s not included, but it should give you a pretty good idea of what the phone code should look like; other than the UI it’s all the code you need.
public class Connection extends Activity implements OnClickListener {
public static final String TAG=”Connection”;
public static final int TIMEOUT=10;
Intent i=null;
TextView tv=null;
private String connectionStatus=null;
private Handler mHandler=null;
ServerSocket server=null;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.connection);
//Set up click listeners for the buttons
View connectButton = findViewById(R.id.connect_button);
connectButton.setOnClickListener(this);
i = new Intent(this, Connected.class);
mHandler=new Handler();
}
@Override
public void onClick(View v) {
switch (v.getId()) {
case R.id.connect_button:
tv = (TextView) findViewById(R.id.connection_text);
//initialize server socket in a new separate thread
new Thread(initializeConnection).start();
String msg=”Attempting to connect…”;
Toast.makeText(Connection.this, msg, msg.length()).show();
break;
}
}
private Runnable initializeConnection = new Thread() {
public void run() {
Socket client=null;
// initialize server socket
try{
server = new ServerSocket(38300);
server.setSoTimeout(TIMEOUT*1000);
//attempt to ccept a connection
client = server.accept();
Globals.socketIn=new Scanner(client.getInputStream());
Globals.socketOut = new PrintWriter(client.getOutputStream(), true);
} catch (SocketTimeoutException e) {
// print out TIMEOUT
connectionStatus=”Connection has timed out! Please try again”;
mHandler.post(showConnectionStatus);
} catch (IOException e) {
Log.e(TAG, “”+e);
} finally {
//close the server socket
try {
if (server!=null)
server.close();
} catch (IOException ec) {
Log.e(TAG, “Cannot close server socket”+ec);
}
}
if (client!=null) {
Globals.connected=true;
// print out success
connectionStatus=”Connection was succesful!”;
mHandler.post(showConnectionStatus);
startActivity(i);
}
}
};
/**
* Pops up a “toast” to indicate the connection status
*/
private Runnable showConnectionStatus = new Runnable() {
public void run() {
Toast.makeText(Connection.this, connectionStatus, Toast.LENGTH_SHORT).show();
}
};
}
3. The host machine application will then obviously implement a client socket. I use a PrintWriter to write stuff to the output stream and a Scanner to parse what’s coming through the input stream. Obviously there are many other ways to handle this.
Here’s the code I used:
/**
* Initialize connection to the phone
*
*/
public void initializeConnection(){
//Create socket connection
try{
socket = new Socket("localhost", 38300);
out = new PrintWriter(socket.getOutputStream(), true);
//in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
sc=new Scanner(socket.getInputStream());
// add a shutdown hook to close the socket if system crashes or exists unexpectedly
Thread closeSocketOnShutdown = new Thread() {
public void run() {
try {
socket.close();
} catch (IOException e) {
e.printStackTrace();
}
}
};
Runtime.getRuntime().addShutdownHook(closeSocketOnShutdown);
} catch (UnknownHostException e) {
Print.fatalError(“Socket connection problem (Unknown host)”+e.getStackTrace());
} catch (IOException e) {
Print.fatalError(“Could not initialize I/O on socket “+e.getStackTrace());
}
}
4. Putting it all together
So, this is what you have to do (in this order).
- The adb port forwarding command must run on the host computer
- The Android application needs to run, setup a server socket on localhost (on the 2nd port used in the adb command) and then wait to get a connection
- The host computer needs to open up a client socket on localhost (on the 1st port used in the adb command) and connect to the Android phone
- Done! Communicate over sockets as usual.
Hope it’s useful to someone out there! If you have problems trying to get this code working, let me know in the comments and I’ll help you out. When I have time, I will try to actually make two small programs that demonstrate the behavior, but it might be a while before I can do that, life has been very busy lately.
Thanks for this post. I am a novice programmer. I get errors in
these statements – “Globals cannot be resolved..”
Globals.socketIn=new Scanner(client.getInputStream());
Globals.socketOut = new PrintWriter(client.getOutputStream(), true);
…..
Globals.connected=true;
please can you help me out.
Hi Carl,
As I said, that sample code above is for illustration only, it will not run by itself because I copied it out of a larger project.
In my project Globals is a class which contains a bunch of global variables, that’s all. Go ahead and remove “Globals.” from all of these and just declare them in your program.
Scanner socketIn; PrintWriter socketOut; boolean connected;
Let me know if you need more help.
If I have time I will write a sample project that you can actually download and run to show how this works.
GL!
a.
Thank you anothem..I’ll try it and let you know.
Thanks so much. It works!
now, that the communication of the pc with the smartphone is established. I’m trying to get a program to send commands to the smartphone, like click events on a specific positions, etc., Any ideas ?
Thanks again..
Np, I’m happy you got it working.
I can’t help you too much with what you’re trying to do there, but I wrote a post about a tool for showing the Android screen just this week (and I think it allows some control as well).
The tool is open source so maybe you want to check it out and see how they solve some of these problems and get some ideas.
Best,
-a.
Hi,
Its look it will help to me. But i want to do pcsync in android through USB with obex. If you have any stuff please help to me.
Thanks
Laxman Dodda
Starting with 2.1 Android supports obex, but that’s all I know about that, haven’t worked with it at all.
Hi,
Can you help to me. How to establish a connection between pc (pcsuite) and target (mobile) in windows environment. Through program. It will be good help. Above is good to me to understand. Please mail a sample program to me.
Regards
Laxman Dodda
thanks for that post. Do you think is possibile to connect via USB an android device with another device that is not a pc with your code?
thanks in advance,
Andrea.
Well, the way it is here I’m using adb to enable communication so you need a computer running adb and able to execute the commands for it. I can’t see how this could be used with another device and there are probably better ways to solve that specific problem.
Thanks.
thanks for your answer. do you have any suggestion? any keyword for a google search?
thanks again
i wrote the code like yours ,but there is error,permission deny.
Runtime.getRuntime().exec(“adb forward tcp:38300 tcp:38300″);
why? should xml add some permission?
li, you might have things confused. The adb runs on the host machine, not on the smartphone.
Hi Anothem,
I got the below exception which I couldnt resolve it…
05-07 20:55:05.079: WARN/System.err(5298): java.io.IOException: Error running exec(). Command: [E:\gingerBread\android-sdk-windows\tools\adb.exe, forward, tcp:5037, tcp:38300] Working Directory: null Environment: null
05-07 20:55:05.079: WARN/System.err(5298): at java.lang.ProcessManager.exec(ProcessManager.java:226)
05-07 20:55:05.079: WARN/System.err(5298): at java.lang.Runtime.exec(Runtime.java:196)
05-07 20:55:05.079: WARN/System.err(5298): at java.lang.Runtime.exec(Runtime.java:285)
05-07 20:55:05.079: WARN/System.err(5298): at java.lang.Runtime.exec(Runtime.java:218)
05-07 20:55:05.079: WARN/System.err(5298): at com.adb.test.ADBTest.execAdb(ADBTest.java:28)
05-07 20:55:05.079: WARN/System.err(5298): at com.adb.test.ADBTest.access$0(ADBTest.java:25)
05-07 20:55:05.079: WARN/System.err(5298): at com.adb.test.ADBTest$1.run(ADBTest.java:18)
05-07 20:55:05.079: WARN/System.err(5298): at java.lang.Thread.run(Thread.java:1096)
05-07 20:55:05.079: WARN/System.err(5298): Caused by: java.io.IOException: Permission denied
05-07 20:55:05.079: WARN/System.err(5298): at java.lang.ProcessManager.exec(Native Method)
05-07 20:55:05.079: WARN/System.err(5298): at java.lang.ProcessManager.exec(ProcessManager.java:224)
05-07 20:55:05.079: WARN/System.err(5298): … 7 more
Please suggest me some solution for it..
Thanks,
Manoj.
Sounds like you have some problems running exec. Try and see if you can run other programs using that command. Also, there shouldn’t be any commas in the command, it would appear from your error that you have that.
GL!
Hi Anothem,
thanks for your reply.
I am trying to write and adroid app which takes the logs…Something like…
in an activity…
I want to run the \”adb logcat\” and want to show it on the textbox. this is what I am trying…any suggestions?
Thanks Anothem,
Just what I was looking for…
Thanks Nicholas, glad to help.
Hello Anothem,
Would it be possible to establish the usb connection and then run telnet commands back to the pc from the phone? Say if you had a telnet daemon running on specified port on the PC?
Hi Scott,
I haven’t tried it, but I don’t see any reason why it couldn’t be done.
–a.
Hi Anothem,
Thanks for your solution.
Great example, it helped me understand several pieces together
Great, work for me also.
We must create server port on Android device reason for this is, we have to use ‘adb forward … ‘ command.
After using this command window can’not bind to same port which is needed for any server.
hi anothem,
can we implement a simple server program in C on android phone cross-compiled for ARM platform in your example? client program is also a C program running on windows PC.
can we do client server communication now after port forwarding through ADB?
Hi dj,
I can’t say for certain what the answer to your question is, because I haven’t done any work with native apps on Android. From what I know of ADB you should be able to leverage it from native apps as well, but that’s something you’ll have to look into.
I’m curious about it, so I’ll do some research into it when I get a chance and I’ll let you know if I find out anything.
Alex
Hi Alex,
Thanks a lot for your reply.:)i will also try along this line and get back here if i succeed..As far as i tried till now its a failure..i dono what im missing in running the server c code in android OS.
Hi dj,
I trying to implement same kind of sever client program in c for android,I hope by this time you might have good command over this topic! Can you share your code in this blog? this would be really great helpful for me move future.
hi anothem,
nice post. finnaly i found example code to connect android USB to pc. but i’m still confused. i have to try and i get some bug. can you give me your source code? please.
thanks before
sasa, check out this post: http://www.anothem.net/archives/2011/11/22/with-our-powers-combined-sample-code/
There’s an external link there to a sample project using these concepts.
can this source code to using send character to windows hyperterminal?
sasa, I’m not familiar with the hyperterminal. But all this code is showing is how to set up a simple socket connection. You can leverage this to implement other communication protocols if you need to.
Hi Mahi,
sorry dint see ur post..normal windows based client C code and server C code in linux worked for me in this regard.
i got the server code from this site
http://www.tidytutorials.com/2010/06/linux-c-socket-example-with-client.html
and cross compiled it for ARM processor.i think this should help
Great post and information. Worked for me.
Thanks a Lot!!
Thank you very much Alex.
Hi, I have found your post very helpful. I need to know the following: I want to build an app that will run on PC and will show the android sensors’ readings on the PC. Is it possible?
Thanks
Thanks Bazil!
It can definitely be done if you have both an Android app (or service maybe?) and a PC app running at the same time, with a connection similar to what I was doing.
Not sure if there’s anyway to leverage adb for this and do what you want without running an app at the same time. I believe not though.
Very good explaination I have ever seen. Got a clear picture of how port forwarding works ! Thanks a lot !!
Great sample. Thank you!
You need to add the required permission on the manifest to be able to run your sample.
<manifest xmlns:android="http://sc…