I need to send few strings on localhost via socket on android using native code (in C particularity) but I've faced weird problem - recv() function always returns -1 and eerno tells "Try again!"
Here is code responsible for initialization of socket and receiving response
void request() {
struct sockaddr_in sa;
memset(&sa, 0, sizeof(sa));
sa.sin_family = AF_INET;
//need to send string to localhost
inet_aton("127.0.0.1", &(sa.sin_addr));
int sock;
char res[7];
sock = socket(AF_INET, SOCK_STREAM, 0);
sa.sin_port = htons(27042);
int connection = connect(sock, (struct sockaddr *) &sa, sizeof sa);
if (connection != -1) { //connection >= 0
memset(res, 0, 7);
send(sock, "\x00", 1, NULL);
send(sock, "AUTH\r\n", 6, NULL);
usleep(100); // Give it some time to answer
int rec = recv(sock, res, 7, MSG_DONTWAIT);
// rec is always -1 and errno says "Try again!"
}
close(sock);
}
There is an INTERNET permission in Manifest file.
I've tried to put recv(sock, res, 7, MSG_DONTWAIT) part in while loop to wait maybe it would return some data but no success. Maybe I need to call something like flush() after send()?
Does any one know where could be trouble?
UPD. This code runs in one android app (client) and tries to send string to other android app that runs on the same device (server).
Solution became pretty obvious - current "server" version can't process "AUTH" message that is why "client" app receive -1 response. I've tried older version and everything worked fine.
Related
I have problems with client/server application that is part of a bigger system for distributed computing. The clients are Android devices that run a native Android NDK application written in C. At some point the clients send registration messages to the server application, which is also written in C and runs on a windows machine.
The weird thing is, right after installing the Android application on the device everything works fine. However, after a while the Socket problem starts. All connect() function calls end with a time out on the client side. The error is not deterministic and occurs at different points in time. To make it work again, I have to uninstall the application in Android manually and reinstall it. After that I works for some time and then the error starts again. The same C code is used on clients that run on normal windows PCs and there the problem does not occur.
The network connection is fine and I checked, if the server ports are open and reachable with the Simple Socket Tester app from the client device. I also gave Android the permission for Internet use and the parameters of the connect() call are correct.
EDIT:
Sorry for the missing code. I thought the error is obvious and based on the different platforms, since it works on windows and I am not that experienced in Android NDK. Here is the code:
int pi_connect(SOCKET s, const SOCKADDR *name, int namelen)
{
int result = connect(s, name, namelen);
if (result < 0) {
ALOG("Socket connecting error!");
return -1;
}
return result;
}
SOCKET pi_socket(int af, int type, int protocol) {
SOCKET returnSocket = socket(af, type, protocol);
int yes = 1;
if (setsockopt(returnSocket, SOL_SOCKET, SO_REUSEADDR, &yes, sizeof(int)) == -1)
{
perror("Server-setsockopt() error!");
exit(1);
}
if (returnSocket < 0) {
ALOG("Socket creation error!");
return -1;
}
return returnSocket;
}
SOCKET setupSendSocket(u_long host, int hostPort) {
SOCKET sendingSocket;
SOCKADDR_IN addr;
sendingSocket = pi_socket(AF_INET, SOCK_STREAM, 0);
memset(&addr, 0, sizeof(SOCKADDR_IN));
addr.sin_family = AF_INET;
addr.sin_port = htons(hostPort);
addr.sin_addr.s_addr = host;
long rc = pi_connect(sendingSocket, (SOCKADDR*) &addr, sizeof(SOCKADDR));
if (rc < 0) {
return 0;
}
return sendingSocket;
}
void requestOwnIP() {
SOCKET connectedIPSocket = setupSendSocket(inet_addr(brokerIP), 34123);
if(connectedIPSocket==0)
return;
sendBHeartbeatMessage(connectedIPSocket);
myIP = receiveBIPMessage(connectedIPSocket);
pi_closesocket(connectedIPSocket);
}
The requestOwnIP() function is called in the main function of the NDK application.
EDIT 2 (some new remarks): After rebooting the device, the connect() is successful again and the system works for some time. Is there something stored in the process table of the operating system, that can cause this problem? I first though that it could be a high amount of sockets that are in the time_wait state, but I added SO_REUSEADDR and the problem is still occurring.
I would really appreciate some help. Thank you in advance!
Regards
Dominik
OS: Android L
Server: an native level system server, service through abstract socket.
Client: jni in normal 3rd APK
Get a 'permission denied' while using APK to connect the socket.
I thought abstract socket has no permissions!
And, the same code works when running in a adb shell, rooted shell.
The question is: where is the permisson set?
the code:
char *target_socket_name = "#mobilelogd";
int sock_id = 0;
struct sockaddr_un sun;
int address_len;
sock_id = socket(AF_UNIX, SOCK_STREAM, 0);
if (sock_id < 0) {
LOG("in %s: Unable to create socket: %s\n", __func__, strerror(errno));
return -1;
} else {
LOG("socket created!\n");
}
memset(&sun, 0, sizeof(sun));
sun.sun_family = AF_UNIX;
strncpy(sun.sun_path, target_socket_name, strlen(target_socket_name));
sun.sun_path[0] = 0;
address_len = offsetof(struct sockaddr_un, sun_path) + strlen(target_socket_name);
if (connect(sock_id, (struct sockaddr *)&sun, address_len) == -1)
{
LOG("in %s: Connect to socket failed: (%d),%s\n", __func__, errno, strerror(errno));
close(sock_id);
return -1;
}
--- EDIT 1 ---: add some initialise code,and change '0' to 0. Same result.
Okay, here is the scoop it changed on L by a bug introduced..the bug fix is the pipeline:
https://android.googlesource.com/device/moto/shamu/+/b2db40f
Until than do java pipes or native pipes instead
Since Android manipulated the Linux kernel and added Paranoid networking to it, So you should add the following permission to your manifest file.
<uses-permission android:name="android.permission.INTERNET" />
Android adds a "paranoid network" option to the Linux kernel, which restricts access to some networking features depending on the group of the calling process.
So, your app's uid (user id; each app is assigned an unique uid once it is installed) must be granted that permission in order to do networking tasks.
I have a usb device which have a button.
And I want to an android app to catch a signal of the button.
I found inferface and endpoint number of the button.
It had seemed to perform ordinarily at galaxy S3 and galaxy note.
But later, I found that it has delay at other phones.
I was able to receive instant responses about 10% of the time; usually there was a 2-second delay, with some cases where the whole response was lost.
Although I couldn't figure out the exact reason, I realized that the phones that had response delays were those with kernel version 3.4 or later.
Here is the code that I used initially.
if(mConnection != null){
mConnection.claimInterface(mInterfaces.get(0), true);
final UsbEndpoint endpoint = mInterfaces.get(0).getEndpoint(0);
Thread getSignalThread = new Thread(new Runnable() {
#Override
public synchronized void run() {
byte[] buffer = new byte[8];
final ByteBuffer byteBuffer = ByteBuffer.wrap(buffer);
while(mConnection!=null){
int len = mConnection.bulkTransfer(endpoint, buffer, buffer.length, 0);
if( len>=0 ){
// do my own code
}
}
}
});
getSignalThread.setPriority(Thread.MAX_PRIORITY);
getSignalThread.start();
}
edit timeout
when the timeout was set to 50ms, I wasn't able to receive responses most of the time. When the timeout was 500ms, I was able to initially get some delayed-responses; however, I lost all responses after several tries with this setting.
Using UsbRequest
In addition to using the bulktransfer method, I also tried using UsbRequest and below is the code that I used.
#Override
public synchronized void run() {
byte[] buffer = new byte[8];
final ByteBuffer byteBuffer = ByteBuffer.wrap(buffer);
UsbRequest inRequest = new UsbRequest();
inRequest.initialize(mConnection, endpoint);
while(mConnection!=null){
inRequest.queue( byteBuffer , buffer.length);
if( mConnection.requestWait() == inRequest ){
// do my own code
}
}
}
However, the same kind of delay happened even after using UsbRequest.
Using libusb
I also tried using libusb_interrupt_transfer from an open source library called libusb.
However this also produced the same type of delay that I had when using UsbDeviceConnection.
unsigned char data_bt[8] = { 0, };
uint32_t out[2];
int transfered = 0;
while (devh_usb != NULL) {
libusb_interrupt_transfer(devh_usb, 0x83, data_bt, 8, &transfered, 0);
memcpy(out, data_bt, 8);
if (out[0] == PUSH) {
LOGI("button pushed!!!");
memset(data_bt, 0, 8);
//(env)->CallVoidMethod( thiz, mid);
}
}
After looking into the part where libusb_interrupt_transfer is processed libusb, I was able to figure out the general steps of interrupt_transfer:
1. make a transfer object of type interrupt
2. make a urb object that points to the transfer object
3. submit the urb object to the device's fd
4. detect any changes in the fd object via urb object
5. read urb through ioctl
steps 3, 4, 5 are the steps regarding file i/o.
I was able to find out that at step 4 the program waits for the button press before moving onto the next step.
Therefore I tried changing poll to epoll in order to check if the poll function was causing the delay; unfortunately nothing changed.
I also tried setting the timeout of the poll function to 500ms and making it always get values of the fd through ioctl but only found out that the value changed 2~3 seconds after pressing the button.
So in conclusion I feel that there is a delay in the process of updating the value of the fd after pressing the button. If there is anyone who could help me with this issue, please let me know. Thank you.
Thanks for reading
I'm trying to send a broadcast message in my ad-hoc network - 192.168.2.x, using native c code.
But the app hangs on sendto(). btw the hang is not connected to the while, that wraps it, as I can see in debug, it only tries sendto() ones and hangs.
Is there something wrong with my code?
int broadcast(char* msg){
int bcast_sock;
struct sockaddr_in their_addr; // connector's address information
if((bcast_sock = socket(AF_INET, SOCK_DGRAM, 0)) == -1)
{
LOGE("ERROR BROADCASTING , socket wasn't created");
}
int broadcastEnable=1;
int ret=setsockopt(bcast_sock, SOL_SOCKET, SO_BROADCAST, &broadcastEnable, sizeof(broadcastEnable));
if(ret < 0)
{
LOGE("ERROR BROADCASTING, Coulnt set broadcast enable through socket options");
}
their_addr.sin_family = AF_INET; // host byte order
their_addr.sin_port = htons(BROADCAST_PORT); // short, network byte order
their_addr.sin_addr.s_addr = htonl(INADDR_BROADCAST);
memset(&(their_addr.sin_zero), '\0', 8); // zero the rest of the struct
while(-1 == (int)sendto(bcast_sock, msg, strlen(msg), 0,
(struct sockaddr *)&their_addr, sizeof(struct sockaddr)));
return 0;
}
A couple of notes:
This of course are rooted phones.
If I broadcast using java broadcast, it works fine, I'm able to receive the broadcast ie:
datagramSocket.setBroadcast(true);
int receiverPort = 4949;
sendPacket = new DatagramPacket(data, data.length, IPAddress, receiverPort);
Non broadcast messages are also being sent and received using native code.
The CPU usage becomes ~ 95% .
I've also tried simply sending to 192.168.2.255.
any ideas?
I solved it by changing address conversion from:
their_addr.sin_addr.s_addr = htonl(INADDR_BROADCAST);
to
inet_aton(IP,&their_addr.sin_addr);
where IP = "192.168.2.1"
Thanks for the help epx
I don't know if this is in the way I'm handling Android, or a problem with my native code, or both.
I am setting up a udp socket in C++ (wrappers generated by swig):
udpSocket = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
if (udpSocket < 0)
{
pthread_mutex_unlock(&csOpenCloseUdp);
throw IOException("Failed to open socket");
}
char bAllowMultiple = true;
setsockopt(udpSocket, SOL_SOCKET, SO_REUSEADDR, &bAllowMultiple, sizeof(bAllowMultiple));
setsockopt(udpSocket, IPPROTO_IP, IP_MULTICAST_TTL, (char *)&hopLimit, sizeof(hopLimit));
setsockopt(udpSocket, IPPROTO_IP, IP_MULTICAST_IF, (char *)&localAddr, sizeof(localAddr));
// Set to non-blocking mode
unsigned long bMode = 1;
ioctl( udpSocket, FIONBIO, &bMode );
// Create the local endpoint
sockaddr_in localEndPoint;
localEndPoint.sin_family = AF_INET;
localEndPoint.sin_addr.s_addr = localAddr.s_addr;
localEndPoint.sin_port = groupEndPoint.sin_port;
// Bind the socket to the port
int r = bind(udpSocket, (sockaddr*)&localEndPoint, sizeof(localEndPoint));
if (r == SOCKET_ERROR)
{
//LeaveCriticalSection(&csOpenCloseUdp);
pthread_mutex_unlock(&csOpenCloseUdp);
close();
throw IOException("Failed to bind port");
}
// Join the multicast group
struct ip_mreq imr;
imr.imr_multiaddr = groupEndPoint.sin_addr;
imr.imr_interface.s_addr = localAddr.s_addr;
setsockopt(udpSocket, IPPROTO_IP, IP_ADD_MEMBERSHIP, (char*)&imr, sizeof(imr));
The socket is not throwing any exceptions, and after this it has some value not INVALID_SOCKET.
When I try to send a packet though,
int r = sendto(udpSocket, (char*)dataToSend, (size_t)length, 0, (sockaddr*)&groupEndPoint, (socklen_t)sizeof(groupEndPoint));
I get errno 101: Network is unreachable.
I'm quite new to socket programming, and I know sockets in Android is a bad way to start, but the fact is I have to get this done and have very little time. Does anyone here know of a likely reason to get Network Unreachable? Has anyone tried playing with UDP on Android and can shed some light?
Is there a requirement to use C++ sockets? If possible, in the interests of time, and pretty much
in the interests of everything, I'd recommend the Java API instead. Here is an example of how to use it: http://android-er.blogspot.com/2011/01/simple-communication-using.html . I like C, but I would recommend against using it here.
SOLVED:
I just had to monkey with the ethernet settings on the device to get it to talk to my laptop. for some reason it didn't like using the dedicated link, so I'm going through the local network router and it's working. now getting different issues, but this one's done