My tethering app sometimes does not get internet access. In these cases Windows will not ask whether the app has permission to use the internet. My app generates no errors but of course will not tether.
How can I test whether my Delphi app has access to the internet sufficient for tethering?
The following code should work on all platforms:
uses IdTCPClient;
function CheckInternet : Boolean;
var TCPClient : TIdTCPClient;
begin
TCPClient := TIdTCPClient.Create (NIL);
try
try
TCPClient.ReadTimeout := 2000;
TCPClient.ConnectTimeout := 2000;
TCPClient.Port := 80;
TCPClient.Host := 'google.com';
TCPClient.Connect;
TCPClient.Disconnect;
Result := true;
except
Result := false;
end; { try / except }
finally
TCPClient.Free;
end; { try / finally }
end;
Source: www.fmxexpress.com
A library to check for an Internet connection on mobile devices can be found at www.delphiworlds.com
Related
I'm trying to implement UDP Hole Punching with Delphi with Indy and Firemonkey technology.
I have tried to follow this document: https://www.researchgate.net/publication/1959162_Peer-to-Peer_Communication_Across_Network_Address_Translators
The program seems to work but is NOT stable.
If I work on a system on the local intranet no problem.
If I work on an internet, it doesn't always work and I don't know why.
I have created two applications.
The first is server side.
Everytime all clients connect correctly to server.
The server registers the Local IP and Internet IP pairs in a variable (fPeers).
I created an IdUDPServer instance.
This is the “Connect push button” code:
procedure TForm1.B_ConnectClick(Sender: TObject);
var
vIdSocketHandle: TIdSocketHandle;
begin
if IdUDPServer.Active then
begin
IdUDPServer.Active := False;
B_Connect.Text := 'Connect';
end
else
begin
IdUDPServer.Bindings.Clear;
vIdSocketHandle := IdUDPServer.Bindings.Add;
vIdSocketHandle.IP := GStack.LocalAddress;
vIdSocketHandle.Port := E_POrt.Text.ToInteger;
IdUDPServer.Active := True;
B_Connect.Text := 'Disconnect';
end;
end;
During the IdUDPServerUDPRead event I capture the Local and Internet IP addresses of the clients that connect.
In the TStringLIST called fPeerIP I add the list of addresses.
procedure TForm1.IdUDPServerUDPRead(AThread: TIdUDPListenerThread;
const AData: TIdBytes; ABinding: TIdSocketHandle);
var vPair: string;
vData: string;
vString: string;
vLog: string;
begin
vPair := ABinding.PeerIP + ':'+ABinding.PeerPort.ToString;
vData := BytesToString(AData);
vLog := '';
if leftstr(vdata,7) = 'LOCALIP' then
begin
vString := vPair+#9+lsExtract(vData,2,',');
if fPeerIP.IndexOfName(vString) = -1 then
begin
fPeerIP.Add(vString);
M_Peers.Lines.Add(vString);
vLog := vLog + vString + #13#10;
IdUDPServer.Send(ABinding.PeerIP, ABinding.PeerPort, 'Peer aggiunto alla lista');
end;
end
else vLog := vData;
end;
On the client side, I created an IdUDPServer instance which, upon connection, sends a string to the server.
procedure TForm2.B_ConnectClick(Sender: TObject);
var vIdSocketHandle: TIdSocketHandle;
vLocalAddressList: TIdStackLocalAddressList;
vI: Integer;
vSendLIST: TStringLIST;
begin
if IdUDPServer.Active then
begin
Timer.Enabled := False;
IdUDPServer.Active := False;
B_Connect.Text := 'Connect';
M_Networks.Lines.Clear;
M_Debug.Lines.Clear;
LB_Peers.Items.Clear;
end
else
begin
try
vSendLIST := TStringLIST.Create;
IdUDPServer.Bindings.Clear;
vLocalAddressList := TIdStackLocalAddressList.Create;
GStack.GetLocalAddressList(vLocalAddressList);
M_Networks.Lines.Clear;
for vI := 0 to vLocalAddressList.Count-1 do
begin
if vLocalAddressList.Addresses[vI].IPVersion = id_IPV4 then
begin
M_Networks.Lines.Add(vLocalAddressList.Addresses[vI].IPAddress);
vSendLIST.Add(Format('LOCALIP,%s:%d',[vLocalAddressList.Addresses[vI].IPAddress,E_ClientPort.Text.ToInteger]));
end;
end;
vIdSocketHandle := IdUDPServer.Bindings.Add;
vIdSocketHandle.Port := E_ClientPort.Text.ToInteger;
vIdSocketHandle.IP := '0.0.0.0';
IdUDPServer.Active := True;
for vI := 0 to vSendLIST.Count-1 do
IdUDPServer.Send(E_Server.Text, E_Port.Text.ToInteger, vSendLIST[vI]);
B_Connect.Text := 'Disconnect';
if Assigned(vSendLIST) then FreeAndNil(vSendLIST);
finally
if Assigned(vLocalAddressList) then FreeAndnil(vLocalAddressList);
end;
end;
end;
Also on the client side, in the IdUDPServerUDPRead event I detect the list of Peers (function sent by the server) and send a "PING" to each connected peer.
I realize maybe I have given little information.
I'd like to know your opinion and possibly indicate to me if I made a mistake in the process that activates the Hole Punching.
Thanks in advance
LS
Your code is theoretically right and may work on some NAT routers but it will not work on the rest
I have been trying to achieve UDP Hole Punching for many years but it's really complicated,
you need to combine many NAT Traversal mechanisms together to make it work in the most cases
Reading about STUN, TURN and ICE mechanisms may help
The following code always returns True on my system:
uses
WinInet;
function CheckInternetConnection() : Boolean;
var
dwConnectionTypes: Integer;
begin
dwConnectionTypes := (
INTERNET_CONNECTION_MODEM +
INTERNET_CONNECTION_LAN +
INTERNET_CONNECTION_PROXY); // "dwConnectionTypes" now "7"
if (InternetGetConnectedState(#dwConnectionTypes, 0)) then
Result := True // Always hit, "dwConnectionTypes" now "18"
else
Result := False; // Never reaches here!
end;
I've tried:
* unplugging the network cable
* stopped "Wireless Zero Configuration" service
* disabled all connections in Control Panel > Network Connections
* definitely confirmed no internet connection in a web browser
What am I missing?
UPDATE
I've confirmed that dynamically loading wininet.dll and using GetProcAddress to find the method "InternetGetConnectedState" gives exactly the same result with the internet disconnected (returns True and the parameter is set to "18").
If you want to know if you are connected to the Internet, there is no other way that contacting a host on the internet.
Correct technically then you only know if that host is online, but that's often good enough, since if your program requires internet access it's because you need to cantact a host on the internet.
One way of doing that is using a TIdHTTP from Indy:
uses
IdHTTP;
uses
IdHTTP;
function HasInternet: Boolean;
begin
with TIdHTTP.Create(nil) do
try
try
HandleRedirects := True;
Result := Get('http://www.Google.com/') <> '';
except
Result := false;
end;
finally
free;
end;
end;
And then use it :
procedure TForm1.FormCreate(Sender: TObject);
begin
Caption := BoolToStr(HasInternet, True);
end;
But it would be bettet to try to contact you host.
In which event or how can i check for internet connections while program is running? Scenario: program is running and suddenly internet connection goes off and a dialog opens "No internet access, changing connection string to central database". I tried this function, but im not sure in which event should i put so that it works all the time.
function TFK_Lib.CheckInternet: boolean;
begin
ConnectedState := INTERNET_CONNECTION_MODEM;
Result := InternetGetConnectedState(#ConnectedState, 0);
end;
You can use a timer to check (at a time period) the connection and show the dialog (as a modal so you can't do anything else).
You can do a practical test and ping google.com.
If I understood your question correctly I thinks its not a bad option.
Code example:
class function TAuthUserFunctions.CheckInternet: boolean;
var
idtcp : TIdTCPClient;
begin
try
idtcp := TIdTCPClient.Create(Nil);
try
idtcp.ReadTimeout := 2000;
idtcp.ConnectTimeout := 2000;
idtcp.Port := 80;
idtcp.Host := 'google.com';
idtcp.Connect;
idtcp.Disconnect;
Result := True;
finally
idtcp.Free;
end;
except
Result := False;
end;
end;
I think this is an easy question for someone familiar with Indy. I'm using Delphi 2010 and Indy 10. I am trying to get off the ground accessing an SSL web service. I think it will be a lot easier if I can get Fiddler to see my HTTP traffic. I have seen posts on StackOverflow that indicate it's no big thing to get Fiddler to see your Indy traffic, that you just have to configure the port to make it work. My question is how do you do that?
Here is my code so far:
procedure TForm1.Button1Click(Sender: TObject);
var slRequest: TStringList;
sResponse,
sFileName: String;
lHTTP: TIdHTTP;
lIOHandler: TIdSSLIOHandlerSocketOpenSSL;
begin
sFileName := 'Ping.xml';
slRequest := TStringList.Create;
try
slRequest.LoadFromFile(sFileName);
lHTTP := TIdHTTP.Create(nil);
lHTTP.Intercept := IdLogDebug1;
lIOHandler := TIdSSLIOHandlerSocketOpenSSL.Create(nil);
try
lHTTP.IOHandler := lIOHandler;
sResponse := lHTTP.Post('https://FSETTESTPROD.EDD.CA.GOV/fsetservice', slRequest);
Memo1.Lines.Text := sResponse;
finally
lIOHandler.Free;
end;
finally
slRequest.Free;
end;
end;
Edit: If I don't use the proxy for Fiddler and click the button while Wireshark is running, I get this traffic in Wireshark.
You can set Indy to use the proxy fiddler provides easily by setting the ProxyParams:
try
lHTTP.IOHandler := lIOHandler;
lHTTP.ProxyParams.ProxyServer := '127.0.0.1';
lHTTP.ProxyParams.ProxyPort := 8888;
sResponse := lHTTP.Post('<URL>', slRequest);
Memo1.Lines.Text := sResponse;
finally
lIOHandler.Free;
end;
You should be able to see all traffic in Fiddler then.
Edit: If that does not work you can add a TIdLogDebug component and add it as interceptor (like you did in your question).
The OnReceive and OnSend events contain the complete headers sent and received aswell as the reply data:
procedure TForm10.captureTraffic(ASender: TIdConnectionIntercept;
var ABuffer: TArray<Byte>);
var
i: Integer;
s: String;
begin
s := '';
for i := Low(ABuffer) to High(ABuffer) do
s := s + chr(ABuffer[i]);
Memo1.Lines.Add(s);
end;
Is there a more elegant way of checking if a TCP port is available with Delphi other than catching a netstat call?
I guess you can use Indy's components to do that. For instance a TIdHTTPServer will raise an exception if a port is in use when it is being opened.
So basically you could create such component, bind it to localhost:<yourport> and if an exception is raised ( catch it and check it ) then the port is probably in use, else it is free.
I guess other indy components can tell if a port is open or not, but I can't look at it right now.
This was just to give you an approach.
#Mattl, if Available means open for you, you can use this code.
program CheckTCP_PortOpen;
{$APPTYPE CONSOLE}
uses
Winsock; //Windows Sockets API Unit
function PortTCPIsOpen(dwPort : Word; ipAddressStr:string) : boolean;
var
client : sockaddr_in;//sockaddr_in is used by Windows Sockets to specify a local or remote endpoint address
sock : Integer;
begin
client.sin_family := AF_INET;
client.sin_port := htons(dwPort);//htons converts a u_short from host to TCP/IP network byte order.
client.sin_addr.s_addr := inet_addr(PChar(ipAddressStr)); //the inet_addr function converts a string containing an IPv4 dotted-decimal address into a proper address for the IN_ADDR structure.
sock :=socket(AF_INET, SOCK_STREAM, 0);//The socket function creates a socket
Result:=connect(sock,client,SizeOf(client))=0;//establishes a connection to a specified socket.
end;
var
ret : Integer;
wsdata : WSAData;
begin
Writeln('Init WinSock');
ret := WSAStartup($0002, wsdata);//initiates use of the Winsock
if ret<>0 then exit;
try
Writeln('Description : '+wsData.szDescription);
Writeln('Status : '+wsData.szSystemStatus);
if PortTCPIsOpen(80,'127.0.0.1') then
Writeln('Open')
else
Writeln('Close');
finally
WSACleanup; //terminates use of the Winsock
end;
Readln;
end.
netstat information can be retrieved by calling the GetTcpTable and GetUdpTable functions in the IP Helper API, or IPHLPAPI.DLL. For more information on calling the IPHLPAPI.DLL from Delphi, check out this Network traffic monitor. There are some wrappers for it too, and it is part of JEDI API Library.
I wrote a Delphi version of NetStat long ago, but have since lost the source code. Those resources should get you started though.
The following code from Synapse works very well:
uses
blcksock;
function PortAvailable(Port:STring):boolean;
var
svr : TTCPBlockSocket;
begin
svr := TTCPBlockSocket.Create;
try
svr.Bind('0.0.0.0',Port);
svr.Listen;
result := svr.LastError = 0;
Svr.CloseSocket;
finally
svr.Free;
end;
end;
Using an Indy.Sockets v10 TIdTCPServer component:
function TExample.IsTCPPortAvailable(const APort: Word): Boolean;
var
LTCPServer: TIdTCPServer;
LBinding: TIdSocketHandle;
begin
Result := True;
LTCPServer := TIdTCPServer.Create;
try
try
with LTCPServer do
begin
DefaultPort := APort;
LBinding := Bindings.Add;
LBinding.IP := '127.0.0.1';
LBinding.Port := APort;
OnExecute := TCPServerExecute;
Active := True;
end;
finally
LTCPServer.Free;
end;
except on EIdCouldNotBindSocket do
Result := False;
end;
end;
procedure TExample.TCPServerExecute(AContext: TIdContext);
begin
end;
Based on Silver's example above, and since in many cases you want to find an available port rather than just verifying that a given port is in use:
uses
//Indy V10
IdContext,
IdSocketHandle,
IdTcpServer;
type
//our port-checking tool
TPortChk = class(TIdTCPServer)
procedure OnExec(AContext: TIdContext);
end;
procedure TPortChk.OnExec(AContext: TIdContext);
begin
//does nothing, but must exist and be hooked
end;
//check a TCP port to see if it's already in use.
//normally used before opening a listener.
function PortAvailable(APort: Word): Boolean;
var
svr: TPortChk;
bnd: TIdSocketHandle;
begin
//assume our port is available
Result := True;
//create our checking object
svr := TPortChk.Create;
try
//set the execute event
svr.OnExecute := svr.OnExec;
//loop looking for an available port
try
//set up the binding for our local system and the
//port in question
bnd := svr.Bindings.Add;
bnd.IP := '127.0.0.1';
bnd.Port := APort;
//try to bind. This will throw an EIdCouldNotBindSocket
//exception if the port is already in use.
svr.Active := True;
//if we get here, the port is *currently* available.
//close the server and bail
svr.Active := False;
Exit;
except
//whoops, port's in use (or some related failure)
Result := False;
end;
finally
svr.Free;
end;
end;
//search a range of ports for the first available
function FindAvailablePort(First, Count: Word): Word;
var
svr: TPortChk;
bnd: TIdSocketHandle;
begin
//assume our initial port is available
Result := First;
//create our checking object
svr := TPortChk.Create;
try
//set the execute event
svr.OnExecute := svr.OnExec;
//loop looking for an available port
while (Result - First) < Count do begin
try
//set up the binding for our local system and the
//port in question
bnd := svr.Bindings.Add;
bnd.IP := '127.0.0.1';
bnd.Port := Result;
//try to bind. This will throw an EIdCouldNotBindSocket
//exception if the port is already in use.
svr.Active := True;
//if we get here, we found our available port, so kill the
//server and bail
svr.Active := False;
Exit;
except
Inc(Result);
svr.Bindings.Clear;
end;
end;
//if we get here, all of our possible ports are in use,
//so return $FFFF to indicate that no port is available
Result := $FFFF;
finally
svr.Free;
end;
end;