Delphi programming to implement Ping operation

Delphi programming to implement Ping operation

Zhang Taili

Users who have used the Internet are familiar with the "Ping" command. It is an executable file under DOS. It is generally used to check the quality of the network connection. The basic principle is to use a function in the ICMP protocol in the TCP/ip protocol package, that is, to send a request to the specified computer, and the computer that receives the request returns a response to determine whether the computer is running on the Internet or to check the network. Is the connection stable and reliable? During the execution of the Ping program, both computers consume very little resources, so it is a very practical tool.

We can implement the "Ping" operation through programming and improve it so that it has a Windows interface style and the display is more intuitive than DOS.

First, a brief explanation of the dynamic link library needed in programming: In the System directory of Windows, you can find the Icmp.dll file. This dynamic link library provides all the functions of the ICMP protocol. Our programming is based on this On the call of dynamic link library.

The calling functions in the Icmp.dll file are described as follows:

1. IcmpCreateFile

Opens a handle through which you can send ICMP request echo messages.

2. IcmpCloseHandle

Close the handle you opened through the IcmpCreateFile function.

3. IcmpSendEcho

Send an ICMP request through the handle you opened and return after timeout or response message reception. Its parameters are basically consistent with its frame structure. Please refer to the program part below. For its specific meaning, you can refer to books on the ICMP protocol.

After a preliminary understanding of the above three functions, we can start programming.

First, our program should have the basic functions shown in Figure 1 after running. To do this, we can first put the controls shown in the upper right picture in the Delphi window, such as buttons, edit boxes, and text display boxes.

(G72.JPG)

Schematic diagram of routine operation

Then, WinSocket is initialized at the beginning of the program (FormCreate). Its function is to declare the version information used and at the same time call the Icmp.dll library.

type

PIPOptionInformation = ^TIPOptionInformation;

TIPOptionInformation = packed record

TTL: Byte;

TOS: Byte;

Flags: Byte;

OptionsSize: Byte;

OptionsData: PChar;

end;

PIcmpEchoReply = ^TIcmpEchoReply;

TICmpEchoReply = packed record

Address: DWord;

Status: DWORD;

RTT: DWORD;

DataSize: Word;

Reserved: Word;

Data: Pointer;

Options: TIPOptionInformation;

end;

TICmpCreateFile = function: THandle; stdcall;

TICmpCloseHandle = function(IcmpHandle: THandle): Boolean; stdcall;

TicmpSendEcho = function(IcmpHandle:THandle;

DestinationAddress: DWORD;

RequestData: Pointer;

RequestSize: Word;

RequestOptions: PIPOptionInformation;

ReplyBuffer: Pointer;

ReplySize: DWord;

Timeout: DWord

): DWord; stdcall;

TMyPing = class(TForm)

Panel1: TPanel;

Label1: TLabel;

PingEdit: TEdit;

ExeBtn: TButton;

Button2: TButton;

Button3: TButton;

StatusShow: TMemo;

PRocedure Button3Click(Sender: TObject);

procedure FormCreate(Sender: TObject);

procedure ExeBtnClick(Sender: TObject);

private

{Private declarations}

hICMP: THANDLE;

IcmpCreateFile:TIcmpCreateFile;

IcmpCloseHandle: TicmpCloseHandle;

IcmpSendEcho: TicmpSendEcho;

public

{Public declarations}

end;

procedure TMyPing.FormCreate(Sender: TObject);

var

WSAData: TWSAData;

hICMPdll: HMODULE;

begin

WSAStartup($101, WSAData);

// Load the icmp.dll stuff

hICMPdll := LoadLibrary('icmp.dll');

@ICMPCreateFile := GetProcAddress(hICMPdll, 'IcmpCreateFile');

@IcmpCloseHandle := GetProcAddress(hICMPdll, 'IcmpCloseHandle');

@IcmpSendEcho := GetProcAddress(hICMPdll, 'IcmpSendEcho');

hICMP := IcmpCreateFile;

StatusShow.Text := ';

StatusShow.Lines.Add('Destination IP address bytes return time (milliseconds)');

end;

Next, it is time to carry out the actual programming process of the Ping operation as shown below.

procedure TMyPing.ExeBtnClick(Sender: TObject);

var

IPOpt:TIPOptionInformation;//IP Options for packet to send

FIPAddress:DWORD;

pReqData,pRevData:PChar;

pIPE:PIcmpEchoReply;//ICMP Echo reply buffer

FSize: DWORD;

MyString:string;

FTimeOut:DWORD;

BufferSize:DWORD;

begin

if PingEdit.Text <> ' then

begin

FIPAddress := inet_addr(PChar(PingEdit.Text));

FSize := 40;

BufferSize := SizeOf(TICMPEchoReply) + FSize;

GetMem(pRevData,FSize);

GetMem(pIPE,BufferSize);

FillChar(pIPE^, SizeOf(pIPE^), 0);

pIPE^.Data := pRevData;

MyString := 'Hello,World';

pReqData := PChar(MyString);

FillChar(IPOpt, Sizeof(IPOpt), 0);

IPOpt.TTL := 64;

FTimeOut := 4000;

IcmpSendEcho(hICMP, FIPAddress, pReqData, Length(MyString), @IPOpt, pIPE, BufferSize, FTimeOut);

if pReqData^ = pIPE^.Options.OptionsData^ then

begin

StatusShow.Lines.Add(PChar(PingEdit.Text) + ' ' +IntToStr(pIPE^.DataSize) + ' ' +IntToStr(pIPE^.RTT));

end;

FreeMem(pRevData);

FreeMem(pIPE);

end

end;

Through the above programming, we have realized the interface operation of the Ping function. In fact, there are many functions of the ICMP protocol, which can be realized through function calls to Icmp.dll.