How send message by idtcpclient to idtcpserver

Simplest form

Client Code

***************UNIT CODE**********************
unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
  StdCtrls, IdBaseComponent, IdComponent, IdTCPConnection, IdTCPClient;

type
  TForm1 = class(TForm)
    Edit1: TEdit;
    IdTCPClient1: TIdTCPClient;
    Button1: TButton;
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.DFM}

procedure TForm1.Button1Click(Sender: TObject);
begin
      try
        IdTCPClient1.Connect;
    if IdTCPClient1.Connected then
          IdTCPClient1.WriteLn(edit1.text);
    IdTCPClient1.Disconnect;
  except
  end;
end;

end.

************FORM CODE*********************
object Form1: TForm1
  Left = 48
  Top = 176
  Width = 312
  Height = 143
  Caption = 'Form1'
  Color = clBtnFace
  Font.Charset = DEFAULT_CHARSET
  Font.Color = clWindowText
  Font.Height = -11
  Font.Name = 'MS Sans Serif'
  Font.Style = []
  OldCreateOrder = False
  PixelsPerInch = 96
  TextHeight = 13
  object Edit1: TEdit
    Left = 40
    Top = 12
    Width = 221
    Height = 21
    TabOrder = 0
    Text = 'Message To Send'
  end
  object Button1: TButton
    Left = 108
    Top = 44
    Width = 75
    Height = 25
    Caption = 'Button1'
    TabOrder = 1
    OnClick = Button1Click
  end
  object IdTCPClient1: TIdTCPClient
    MaxLineAction = maException
    Host = '127.0.0.1'
    Port = 7777
    Left = 40
    Top = 40
  end
end

Save project as client and build

SERVER CODE

****************UNIT CODE********************

unit Unit2;

interface

uses
  Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
  StdCtrls, IdBaseComponent, IdComponent, IdTCPServer;

type
  TForm1 = class(TForm)
    IdTCPServer1: TIdTCPServer;
    Label1: TLabel;
    procedure IdTCPServer1Execute(AThread: TIdPeerThread);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.DFM}

procedure TForm1.IdTCPServer1Execute(AThread: TIdPeerThread);
begin
      Label1.caption:=AThread.Connection.ReadLn;
end;

end.

*******************FORM CODE*****************
object Form1: TForm1
  Left = 131
  Top = 316
  Width = 395
  Height = 85
  Caption = 'Server'
  Color = clBtnFace
  Font.Charset = DEFAULT_CHARSET
  Font.Color = clWindowText
  Font.Height = -11
  Font.Name = 'MS Sans Serif'
  Font.Style = []
  OldCreateOrder = False
  PixelsPerInch = 96
  TextHeight = 13
  object Label1: TLabel
    Left = 64
    Top = 8
    Width = 32
    Height = 13
    Caption = 'Label1'
  end
  object IdTCPServer1: TIdTCPServer
    Active = True
    Bindings = <>
    CommandHandlers = <>
    DefaultPort = 7777
    Greeting.NumericCode = 0
    MaxConnectionReply.NumericCode = 0
    OnExecute = IdTCPServer1Execute
    ReplyExceptionCode = 0
    ReplyTexts = <>
    ReplyUnknownCommand.NumericCode = 0
    Left = 16
    Top = 4
  end
end

save and build as server


then run the server

run the client and click the button

regards