I'm trying to get TXT Records from Wifi Direct Printers nearby. So far, I can discover peers and establish a connection. But no luck with TXT Records.
I tried Wifi Direct Service Discovery, and I believe I did everything properly since I compared lots of codes from different resources including sample projects from Google and some open source Wifi Direct Wrappers in GitHub. But I couldn't make it work.
I've also seen some weird issues while trying to achieve that. e.g in some devices, when I start the peer discovery, Wifi Connection started to be turned off and on constantly.
Can someone explain how this actually works ? are DnsSdServiceResponseListener and DnsSdTxtRecordListener made for Android devices rather than Printers ?
I've also tried to listen the MultiCast DNS IP Address (224.0.0.251) with a MulticastSocket after establishing the connection between Android and Wifi Direct Printer, but I couldn't receive any data as well.
Thanks.
I used "DnsSdServiceResponseListener" and "DnsSdTxtRecordListener" successfully in my current project. Both listeners are associated to discovering local services nearby.
To use them properly, you have to do the following:
Implement your listeners
WifiP2pManager.DnsSdServiceResponseListener dnsListener = new WifiP2pManager.DnsSdServiceResponseListener() {
#Override
public void onDnsSdServiceAvailable(String instanceName, String registrationType, WifiP2pDevice device) {
// instanceName is service name and device is the print information
}};
WifiP2pManager.DnsSdTxtRecordListener txtListener = new WifiP2pManager.DnsSdTxtRecordListener() {
#Override
public void onDnsSdTxtRecordAvailable(String fullDomain, Map record, WifiP2pDevice device) {
// here we get the service published information in the record map object
}};
Add the listeners to your WiFiManager object
wifiP2PManagerObj.setDnsSdResponseListeners(mChannel, dnsListener, txtListener);
Add service request
WifiP2pDnsSdServiceRequest serviceRequest = WifiP2pDnsSdServiceRequest.newInstance();
wifiP2PManagerObj.addServiceRequest(mChannel,serviceRequest, actionListener);
Finally, discover services
wifiP2PManagerObj.discoverServices(mChannel,actionListener);
After discover services is executed successfully, the listeners should receive the nearby services information.
Hope this helps.
Goodluck.
Update
Wifi direct supported printers don't have any published services by default. To use them you have to connect to them via wifi direct and print normally as its a printer connected to your network. Note that those listeners are meant to capture published services (i.e will not capture anything for any device unless its publishing a service).
I think you will need to run Bonjour discovery once the connection is established. You can see NSD and look for "_ipp._tcp" as the service type. By the way,
for "I've also seen some weird issues while trying to achieve that. e.g in some devices, when I start the peer discovery, Wifi Connection started to be turned off and on constantly." if you're testing on a 7.1 device you might be seeing this issue, for which a patch should be coming soon.
Related
I am tring to setup WIFI P2P on 2 devices using
manager.addLocalService(channel, service, ActionListener)
and then connect both devices using
manager.connect(channel, config, ActionListener).
I would like to know which method is called before the popup to accept/reject connection is shown on the target device. All I was able to find was onConnectionInfoAvailable(WifiP2pInfo p2pInfo), but it is called after the connection is established.
I basically want to receive the "instance name" of the device trying to connect to me using WIFI P2P and then reject the connection request without showing system dialog(that allows the user to accept/reject connection).
I can't anything that can help me do this on docs or any other place. If anyone knows how to do it or can point me in the right direction then please let me know.
I solved it. I can put the instancename and devicename (of device I want to connect to) in Map that is passed when setting up service. From other device I can retrieve map of all devices available using this and find the instancename of one I need.
I need to connect 20+ android devices in a client-server network. Each client Android device will be communicating with the server Android device and vice versa. The client devices do not need to communicate with each other.
The server device would need access to internet for a brief period while connected to the clients.
My question is, can Wi-Fi P2P support that many connections reliably? And if yes, how do I go about implementing them?
Or will I have to ensure that all devices are on the same WLAN?
From experience, in a real-world deployment of an Android Wi-Fi Direct application, 20 devices should not be an issue.
Theoretically, the maximum number of devices in a Wi-Fi P2P group, where the GO is an Android device, is 254. The group owner is assigned the IP, 192.168.49.1. Clients are assigned an IP from the range, 192.168.49.2 to 192.168.49.254.
The group owner address is defined by the following in WifiP2pServiceImpl.java:
/* Is chosen as a unique address to avoid conflict with
the ranges defined in Tethering.java */
private static final String SERVER_ADDRESS = "192.168.49.1";
Determining the range for the clients is done as follows:
In WifiP2pServiceImpl.java, the startDhcpServer(String intf) method will start the DHCP server for a given interface - not a surprise. This method is called when the group has started and the device is the group owner.
Taking a closer look at this code, we can see that on the InterfaceConfiguration object, the link address is set to 192.168.49.1 and the prefix length is 24 (prefix length is the number of bits set in a subnet mask, here equivalent to 255.255.255.0) - this implies the answer, but we can dig a little further.
ifcg = mNwService.getInterfaceConfig(intf);
ifcg.setLinkAddress(new LinkAddress(NetworkUtils.numericToInetAddress(
SERVER_ADDRESS), 24));
ifcg.setInterfaceUp();
mNwService.setInterfaceConfig(intf, ifcg);
Next, the following commands will restart tethering with the DHCP range specified by the String[], tetheringDhcpRanges. The calls of mNwService (Network Management Service) methods will execute the appropriate netd commands.
ConnectivityManager cm = (ConnectivityManager) mContext.getSystemService(
Context.CONNECTIVITY_SERVICE);
String[] tetheringDhcpRanges = cm.getTetheredDhcpRanges();
if (mNwService.isTetheringStarted()) {
if (DBG) logd("Stop existing tethering and restart it");
mNwService.stopTethering();
}
mNwService.tetherInterface(intf);
mNwService.startTethering(tetheringDhcpRanges);
And cm.getTetheredDhcpRanges() is ultimately a reference to the following (ConnectivityManager.getTetheredDhcpRanges() -> ConnectivityService.getTetheredDhcpRanges() -> Tethering.getTetheredDhcpRanges()):
// USB is 192.168.42.1 and 255.255.255.0
// Wifi is 192.168.43.1 and 255.255.255.0
// BT is limited to max default of 5 connections. 192.168.44.1 to 192.168.48.1
// with 255.255.255.0
// P2P is 192.168.49.1 and 255.255.255.0
private String[] mDhcpRange;
private static final String[] DHCP_DEFAULT_RANGE = {
"192.168.42.2", "192.168.42.254", "192.168.43.2", "192.168.43.254",
"192.168.44.2", "192.168.44.254", "192.168.45.2", "192.168.45.254",
"192.168.46.2", "192.168.46.254", "192.168.47.2", "192.168.47.254",
"192.168.48.2", "192.168.48.254", "192.168.49.2", "192.168.49.254",
}
and:
mDhcpRange = context.getResources().getStringArray(
com.android.internal.R.array.config_tether_dhcp_range);
if ((mDhcpRange.length == 0) || (mDhcpRange.length % 2 ==1)) {
mDhcpRange = DHCP_DEFAULT_RANGE;
}
in com.android.server.connectivity.Tethering.
Of course, it is possible for the device manufacturer to change this code, so this is also worth considering.
For those planning to deploy applications where there will be many users, a mechanism to allow a more than one device to be GO is required. If data needs to be synchronised between devices, it is simple to simulate "churn" and have GOs only be a GO for a time period before becoming a client to another GO and synchronising any data.
The max number as far as I know is not specified, so you would need to test that out to be certain. Also there could be differences between hardware.
Anyway, the basic implementation would be rather simple. The server would call GreateGroup, so it would be the Groupowner in all cases. And then start locals service advertising. Clients then would simply look for the advertisement and once they see it, they would start connection process to the server. One the server connection is made over Wifi direct you would simply start socket communications from the client to the server (server would have listening socket on all times).
Note that connection would require user to click on the dialog showed when client tries to connect to the group owner. And if you want to get rid of this. Then you could actually use the Accesspoint created by GreateGroup, and add the access point name as well as the password to the advertising. Then your clients could actually use the accesspoint to connect (like to any Wlan accesspoint)
Note though that the Wifi Direct way, would not interfere with Wifi connections, not would it require it. But the accesspoint way would mean that any existing Wifi connection from the client would be disconnected, and the device thinks that the connection made to the server would provide normal internet connectivity.
Remember that devices don't need to be connected to a network to connect to each other. Wi-Fi Direct allows them to connect directly.
Here is a list of Wi-Fi Direct resources that you may find useful: https://groups.google.com/forum/#!topic/wi-fi-direct/uWpuOzHY6y0
I'd recommend following Android's Service Discovery Demo and try implementing it yourself. And here is the source code for the demo.
Is it possible when scanning for devices/peers with WiFi Direct onDnsSdServiceAvailable, onDnsSdTxtRecordAvailable to scan more than just instanceName, serviceType, deviceNAme e.t.c but a value set by you. What I am saying is if there is any way for me to set a string and then when the host scans the device to scan that as well.
Not when you are scanning for devices/peers as you asked but when you are scanning for Services. Which I guess is what you are doing since you mentioned the corresponding methods.
In the part where you instantiate the Service you can set a record which is a map<String,String>, this record will be send to devices discovering the service in the method onDnsSdTxtRecordAvailable.
So what you should try is setting the record in the WifiP2pDnsSdServiceInfo whit the key's you want and when you are discovering services you should look for the values in the map you get in onDnsSdTxtRecordAvailable.
This is all taken from Using Wi-Fi P2P Services.
I hope this helps
No you can't do this, since WiFi-Direct protocol doesn't support this. Instead, you may embed your string in device/service names.
I want to connect my tablet to my phone using WiFi direct in order to send some data like pictures etc from my phone to tablet.
But I do not want my phone to discover it first i.e I don't wanted to use discoverPeers() method of WiFiP2pManger.
How can I achieve this goal?
In your phone, use createGroups(). This makes your phone become the groupOwner. Then call discoverPeers() in your tablet, it will find your phone without your phone calling discoverPeers().
In your phone:
wifiP2pManager = (WifiP2pManager) context.getSystemService(context.WIFI_P2P_SERVICE);
channel=wifiP2pManager.initialize(context,context.getMainLooper(),null);
wifiP2pManager.createGroup(channel, new WifiP2pManager.ActionListener() {
#Override
public void onSuccess() {
Log.i(TAG,"Creating p2p group");
}
#Override
public void onFailure(int i) {
Log.i(TAG,"Creating group failed, error code:"+i);
}
});
In your tablet, discover peers, request peers and connect peers as normal
In order to establish a WiFi Direct connection both phones should be running WiFi Direct discovery. In other words, they will see each other when they are both scanning for WiFi direct connections at the same time. This is because the way WiFi Direct works is that when phones are scanning for WiFi Direct connections, they will negotiate with the other peers for the role of Access Point or Slave device. Hence both need to call discoverPeers() to become discoverable themselves and find nearby devices.
In your use case you could even build your application using wifi hotspot
This solution doesn't work. In Android both need to be on discovery mode in order to connect.
I'm trying to use WiFi-Direct for connecting multiple devices over wifi in a master-slave style (one to many)- one client creates a group using the "createGroup" function, and all the other clients should connect to the group (manually).
when a client press on a "Discover peers" button, i want to give him a list of all the master peers.
And here is the problem- I can't find a way to differentiate between slave peers and the master peer (the one who initiate the createGroup request).
is there any way to filter out all the slave peers and keep only the master peers?
You should be discovering services rather than peers, though the API does work better if you also do peer discovery, thus here's my proposal for your logic:
With slave:
Start peerDiscovery
When you get Peers changed event, start service discovery (for service_type defined by your master)
Add the discovered services into a selection list as they come (note that they come one by one, and I've seen max 5 seconds between discovered services)
With Master
createGroup
Add local service to advertise that you are the master
Start Peer discovery, and make sure by monitoring the Discovery state changes that it stays on (if it goes off, your service advertisement likely will not be seen by the slaves)
A simple way to achieve this is to do the following: You can set which device to be Group Owner (Master device) by setting the groupOwnerIntent to 15.
WifiP2pConfig config = new WifiP2pConfig();
config.groupOwnerIntent = 15; //Value between 0-15
You also need to change the master's device name to something like "Master"+itsCurrentName. (To change the WiFi Direct device name, check my answer on how to set interface device name of wifi direct)
Now, whenever a new device scans for peers, the results will show which devices are GroupOwners from their name that starts with the word "Master".
This is a simple way to filter out master from slave peers.