Trouble connecting android bluetooth client socket to ubuntu server socket

Question

I am writing an Android app that should exchange data to a server over Bluetooth, with the server side on a PC running Ubuntu, using the bluez library, in C (or C++).

My Android app fails (IOException) when I try to connect to my server socket on the PC.

Here is essentially what I in the java code (in Android, full eclipse project here: http://dl.dropbox.com/u/2968234/ThinBTClient.zip)

private static final UUID MY_UUID = UUID.fromString("00001101-0000-1000-8000-00805F9B34FB");
private static String address = "00:02:72:B2:85:C7";  // Hard coded for simplicity
private BluetoothAdapter mBluetoothAdapter = null;
private BluetoothSocket btSocket = null;

..... 
mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
BluetoothDevice device = mBluetoothAdapter.getRemoteDevice(address);
btSocket = device.createRfcommSocketToServiceRecord(MY_UUID);
btSocket.connect(); // This throws IOException after a timeout of 10seconds or so.

On the server side (in Ubuntu 8.10), I basically set up a Bluetooth server socket, along the lines described in the example bluez/sdp-register.c

Down below is my C++ program. To compile it do

g++ -I/usr/include/glib-2.0/ -I/usr/lib/glib-2.0/include -o bt_server bt_server.cpp -lbluetooth

I can do the reverse succesfully, i.e. create a server socket in Android and connect from Linux, however this is not what I want to do! I think either the problem has to do with my config of Ubuntu but I cannot seem to figure this one out and any help would be greatly appreciated!

#include <stdio.h>
#include <errno.h>
#include <fcntl.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <sys/socket.h>
#include <bluetooth/bluetooth.h>
#include <bluetooth/bluetooth.h>
#include <bluetooth/sdp.h>
#include <bluetooth/sco.h>
#include <bluetooth/sdp_lib.h>
#include <bluetooth/rfcomm.h>
#include <bluetooth/l2cap.h>
#include <glib.h>

sdp_session_t* register_service(uint8_t rfcomm_channel)
{
 // Adapted from http://www.btessentials.com/examples/bluez/sdp-register.c
    uint32_t svc_uuid_int[] = {   0x01110000, 0x00100000, 0x80000080, 0xFB349B5F };
    const char *service_name = "Roto-Rooter Data Router";
    const char *svc_dsc = "An experimental plumbing router";
    const char *service_prov = "Roto-Rooter";

    uuid_t root_uuid, l2cap_uuid, rfcomm_uuid, svc_uuid,
           svc_class_uuid;
    sdp_list_t *l2cap_list = 0,
               *rfcomm_list = 0,
               *root_list = 0,
               *proto_list = 0,
               *access_proto_list = 0,
               *svc_class_list = 0,
               *profile_list = 0;
    sdp_data_t *channel = 0;
    sdp_profile_desc_t profile;
    sdp_record_t record = { 0 };
    sdp_session_t *session = 0;

    // set the general service ID
    sdp_uuid128_create( &svc_uuid, &svc_uuid_int );
    sdp_set_service_id( &record, svc_uuid );

    char str[256] = "";
    sdp_uuid2strn(&svc_uuid, str, 256);
    printf("Registering UUID %s\n", str);

    // set the service class
    sdp_uuid16_create(&svc_class_uuid, SERIAL_PORT_SVCLASS_ID);
    svc_class_list = sdp_list_append(0, &svc_class_uuid);
    sdp_set_service_classes(&record, svc_class_list);

    // set the Bluetooth profile information
    sdp_uuid16_create(&profile.uuid, SERIAL_PORT_PROFILE_ID);
    profile.version = 0x0100;
    profile_list = sdp_list_append(0, &profile);
    sdp_set_profile_descs(&record, profile_list);

    // make the service record publicly browsable
    sdp_uuid16_create(&root_uuid, PUBLIC_BROWSE_GROUP);
    root_list = sdp_list_append(0, &root_uuid);
    sdp_set_browse_groups( &record, root_list );

    // set l2cap information
    sdp_uuid16_create(&l2cap_uuid, L2CAP_UUID);
    l2cap_list = sdp_list_append( 0, &l2cap_uuid );
    proto_list = sdp_list_append( 0, l2cap_list );

    // register the RFCOMM channel for RFCOMM sockets
    sdp_uuid16_create(&rfcomm_uuid, RFCOMM_UUID);
    channel = sdp_data_alloc(SDP_UINT8, &rfcomm_channel);
    rfcomm_list = sdp_list_append( 0, &rfcomm_uuid );
    sdp_list_append( rfcomm_list, channel );
    sdp_list_append( proto_list, rfcomm_list );

    access_proto_list = sdp_list_append( 0, proto_list );
    sdp_set_access_protos( &record, access_proto_list );

    // set the name, provider, and description
    sdp_set_info_attr(&record, service_name, service_prov, svc_dsc);

    // connect to the local SDP server, register the service record,
    // and disconnect
    session = sdp_connect(BDADDR_ANY, BDADDR_LOCAL, SDP_RETRY_IF_BUSY);
    sdp_record_register(session, &record, 0);

    // cleanup
    sdp_data_free( channel );
    sdp_list_free( l2cap_list, 0 );
    sdp_list_free( rfcomm_list, 0 );
    sdp_list_free( root_list, 0 );
    sdp_list_free( access_proto_list, 0 );
    sdp_list_free( svc_class_list, 0 );
    sdp_list_free( profile_list, 0 );

    return session;
}

int main(int argc, char **argv)
{
    int port = 3;
    sdp_session_t* session = register_service(port);


    struct sockaddr_rc loc_addr = { 0 }, rem_addr = { 0 };
    char buf[1024] = { 0 };
    int s, client, bytes_read;
    socklen_t opt = sizeof(rem_addr);
    // allocate socket
    s = socket(AF_BLUETOOTH, SOCK_STREAM, BTPROTO_RFCOMM);
    printf("socket() returned %d\n", s);

    // bind socket to port 1 of the first available
    // local bluetooth adapter
    loc_addr.rc_family = AF_BLUETOOTH;
    loc_addr.rc_bdaddr = *BDADDR_ANY;
    loc_addr.rc_channel = (uint8_t) port;
    int r;
    r = bind(s, (struct sockaddr *)&loc_addr, sizeof(loc_addr));
    printf("bind() on channel %d returned %d\n", port, r);

    // put socket into listening mode
    r = listen(s, 1);
    printf("listen() returned %d\n", r);

    //sdpRegisterL2cap(port);

    // accept one connection
    printf("calling accept()\n");
    client = accept(s, (struct sockaddr *)&rem_addr, &opt);
    printf("accept() returned %d\n", client);

    ba2str( &rem_addr.rc_bdaddr, buf );
    fprintf(stderr, "accepted connection from %s\n", buf);
    memset(buf, 0, sizeof(buf));

    // read data from the client
    bytes_read = read(client, buf, sizeof(buf));
    if( bytes_read > 0 ) {
        printf("received [%s]\n", buf);
    }

    // close connection
    close(client);
    close(s);
    sdp_close( session );

    return 0;
}

Answer 1

Make sure on your Ubuntu server that the server socket you're creating is registered in SDP with the same UUID that your client is trying to connect with.

You can do an sdp lookup/dump with $ sdptool browse 00:02:72:B2:85:C7 but you have to run it from another computer.

Answer 2

If there's a ten second delay before the error occurs then that looks like a timeout making a Bluetooth connection and not a application/etc layer configuration error. Is Bluetooth adapter in your PC in 'connectable' mode? (e.g. does "sudo /usr/sbin/hciconfig " contain PSCAN?)

(BTW sdp_set_service_classes apparently overwrites the previous call to sdp_set_service_id).