IdTCPClient on Android: Connecting to non-active network

[rlebeau]

Code:

if NOT assigned(GStack) then // just checking...

You don't need that check. The GStack pointer is always valid whenever an Indy component is alive.

Code:

Posix.SysSocket.setsockopt(
         IdTCPClient1.Socket.Binding.Handle,
         Id_SOL_SOCKET,
         SO_BINDTODEVICE,
         M.AsAnsi(NetworkData.WIFIInterface).ToPointer^,
         Length(NetworkData.WIFIInterface)+1 // assuming the device name uses ASCII chars only
         )

Not sure if this applies to Android's flavor of Linux, but on some Linux platforms, SO_BINDTODEVICE takes an ifreq struct as input instead of a null-terminated string pointer, eg:

Code:

struct ifreq ifr;
memset(&ifr, 0, sizeof(struct ifreq));
snprintf(ifr.ifr_name, sizeof(ifr.ifr_name), "eth0");
ioctl(fd, SIOCGIFINDEX, &ifr);
setsockopt(fd, SOL_SOCKET, SO_BINDTODEVICE,  (void*)&ifr, sizeof(struct ifreq));

Which would translate to Delphi as (roughly):

Code:

uses
  ... Posix.NetIf, Posix.StrOpts, Posix.SysSocket;

const
  SIOCGIFINDEX = $8933;

var
  ifr: Posix.NetIf.ifreq;

FillChar(ifr, Sizeof(ifr), 0);
StrLCopy(ifr.ifr_name, M.AsAnsi(NetworkData.WIFIInterface).ToPointer, IFNAMSIZ-1);
Posix.StrOpts.ioctl(IdTCPClient1.Socket.Binding.Handle, SIOCGIFINDEX, @ifr);
Posix.SysSocket.setsockopt(IdTCPClient1.Socket.Binding.Handle, Id_SOL_SOCKET, SO_BINDTODEVICE, ifr, SizeOf(ifr))

ERROR: TCPThread: GStack failed: WIFIInterface=wlan0 Length(WIFIInterface)=5: Socket Error # 1

Error #1 is EPERM ("Operation not permitted"). You likely need root/sudo access to your Android device to bind to a specific interface by name.