Android app doesn't seem to connect or send anything



  • I am running networktablet on fedora 18 (compiled from source).

    Seems to start up ok and listens on port 40118. But the android app just doesn't do anything, the linux process never receives anything. I can ping my laptop IP from my android device just fine using a ping app. There is no firewall running on the laptop. I used the laptop IP in the android app network setting. Any suggestion?

    My android device is a Galaxy Note 2.

    [jweiss@blinky driver-uinput]$ strace ./networktablet 
    execve("./networktablet", ["./networktablet"], [/* 49 vars */]) = 0
    brk(0)                                  = 0x2126000
    mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f472c5d2000
    access("/etc/ld.so.preload", R_OK)      = -1 ENOENT (No such file or directory)
    open("/etc/ld.so.cache", O_RDONLY|O_CLOEXEC) = 3
    fstat(3, {st_mode=S_IFREG|0644, st_size=112370, ...}) = 0
    mmap(NULL, 112370, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7f472c5b6000
    close(3)                                = 0
    open("/lib64/libc.so.6", O_RDONLY|O_CLOEXEC) = 3
    read(3, "\177ELF\2\1\1\3\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\20\33\2K1\0\0\0"..., 832) = 832
    fstat(3, {st_mode=S_IFREG|0755, st_size=2071376, ...}) = 0
    mmap(0x314b000000, 3896312, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x314b000000
    mprotect(0x314b1ad000, 2097152, PROT_NONE) = 0
    mmap(0x314b3ad000, 24576, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x1ad000) = 0x314b3ad000
    mmap(0x314b3b3000, 17400, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x314b3b3000
    close(3)                                = 0
    mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f472c5b5000
    mmap(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f472c5b3000
    arch_prctl(ARCH_SET_FS, 0x7f472c5b3740) = 0
    mprotect(0x314b3ad000, 16384, PROT_READ) = 0
    mprotect(0x601000, 4096, PROT_READ)     = 0
    mprotect(0x314ae20000, 4096, PROT_READ) = 0
    munmap(0x7f472c5b6000, 112370)          = 0
    open("/dev/uinput", O_WRONLY|O_NONBLOCK) = 3
    ioctl(3, UI_SET_EVBIT, 0x1)             = 0
    ioctl(3, UI_SET_KEYBIT, 0x14a)          = 0
    ioctl(3, UI_SET_EVBIT, 0x3)             = 0
    ioctl(3, UI_SET_ABSBIT, 0)              = 0
    ioctl(3, UI_SET_ABSBIT, 0x1)            = 0
    ioctl(3, UI_SET_ABSBIT, 0x18)           = 0
    write(3, "Network Tablet\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 1116) = 1116
    ioctl(3, SNDRV_CTL_IOCTL_CARD_INFO or UI_DEV_CREATE, 0x45c) = 0
    socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP) = 4
    bind(4, {sa_family=AF_INET, sin_port=htons(40118), sin_addr=inet_addr("0.0.0.0")}, 16) = 0
    recvfrom(4, 
    


  • Note, when i move my finger around on the phone, the wifi "send/receive" arrows light up, and go dim when I stop. So it seems like at some level the Android app is sending something.



  • doh! After debugging with tcpdump and seeing the packets arriving on my laptop, but nothing happening on networktablet, I started to doubt that the firewall was really off.

    Fedora used to use iptables but shutting that off is not how it works anymore.

    sudo systemctl stop firewalld.service did it.