1. GUI Socket Application
Chapter 08.
GUI Socket Application

2. Understanding the structure and principle of Windows GUI applications
Goal
Understanding the structure and principle of Windows GUI applications
Learning how to make Windows based socket applications
Understanding the structure and principle of dialog based applications
Learning how to make dialog based socket applications

3. Windows GUI Application (1/8)
Features of Windows GUI application
Providing easy graphical user interface using various API (Application Programming Interface)
Operating by using message-driven architecture
Terms
API
Core library provided by Windows OS
Event / message
how windows communicate

4. Windows GUI Application (2/8)
Message-driven architecture ①
System
Message queue
event
Application
message queue #1
message queue #2
message queue #3
...
processing
waiting

5. Event/Message loop

6. Windows GUI Application (3/8)
GUI application code
Message processing depending on the window procedure written by programmer
Unprocessed message is processed by window OS
Terms
message handler
Message handling code
window procedure
A set of message handler

7. Windows GUI Application (4/8)
Code example
#include <windows.h> // ①
LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM); // ②
int APIENTRY WinMain(HINSTANCE hInstance, HINSTANCE,
LPSTR lpCmdLine, int nCmdShow) // ③ {
// window class registration ④
WNDCLASS wndclass;
wndclass.cbClsExtra = 0;
wndclass.cbWndExtra = 0;
wndclass.hbrBackground = (HBRUSH)GetStockObject(WHITE_BRUSH);
wndclass.hCursor = LoadCursor(NULL, IDC_ARROW);
wndclass.hIcon = LoadIcon(NULL, IDI_APPLICATION);
wndclass.hInstance = hInstance;
wndclass.lpszClassName = "MyWindowClass";
wndclass.lpszMenuName = NULL;
wndclass.style = CS_HREDRAW | CS_VREDRAW;
wndclass.lpfnWndProc = (WNDPROC)WndProc;
if(!RegisterClass(&wndclass)) return -1;

8. Windows GUI Application (5/8)
Code example (cont’d)
// Window creation ⑤
HWND hWnd = CreateWindow("MyWindowClass",
"WinApp", WS_OVERLAPPEDWINDOW,
0, 0, 600, 300,
NULL, (HMENU)NULL, hInstance, NULL);
if(hWnd == NULL) return -1;
ShowWindow(hWnd, nCmdShow);
UpdateWindow(hWnd);
// message loop ⑥
MSG msg;
while(GetMessage(&msg, 0, 0, 0) > 0){
TranslateMessage(&msg);
DispatchMessage(&msg); }
return msg.wParam;

9. Windows GUI Application (6/8)
Code example (cont’d)
// window procedure ⑦
LRESULT CALLBACK WndProc(HWND hWnd, UINT uMsg,
WPARAM wParam, LPARAM lParam) {
switch(uMsg){
case WM_CREATE:
return 0;
case WM_SIZE:
case WM_DESTROY:
PostQuitMessage(0); }
return DefWindowProc(hWnd, uMsg, wParam, lParam);

10. Windows GUI Application (7/8)
Message-driven architecture ②
System
Message queue
event
Application
Message queue #1
Message queue #2
Message queue #3
...
application #1
Message
loop
Message handler #1
Message handler #2
Message handler #3
•••
DefWindowProc()
Window procedure

11. Windows GUI Application (8/8)
control
A kind of window provided by windows OS
Input/output and display information
WinApp.cpp

12. windows based socket application
Structure
GUITCPServer.cpp
Thread 1
Message
loop
Message handler #1
Message handler #2
Message handler #3
•••
DefWindowProc()
Window procedure
thread2
thread3
...
Thread n
Window message handling
Socket comm. and data processing

13. Dialog based application (1/4)
A kind of window containing various control
A part of application
Processing user input and output

14. Dialog based application (2/4)
Independent dialog based application

15. Dialog based application (3/4)
Code example
#include <windows.h>
#include "resource.h" // ①
BOOL CALLBACK DlgProc(HWND, UINT, WPARAM, LPARAM); // ②
int APIENTRY WinMain(HINSTANCE hInstance, HINSTANCE,
LPSTR lpCmdLine, int nCmdShow) {
DialogBox(hInstance, MAKEINTRESOURCE(IDD_DIALOG1),
NULL, DlgProc); // ③
return 0; }
BOOL CALLBACK DlgProc(HWND hDlg, UINT uMsg,
WPARAM wParam, LPARAM lParam) // ④

16. Dialog based application (4/4)
Code example (cont’d)
DlgApp.cpp
switch(uMsg){
case WM_INITDIALOG: // ⑤
return TRUE;
case WM_COMMAND: // ⑥
switch(LOWORD(wParam)){
case IDOK:
EndDialog(hDlg, 0); // ⑦
case IDCANCEL:
EndDialog(hDlg, 0); }
return FALSE;

17. Dialog based socket application (1/2)
Structure
Same as general GUI socket application
dialog message handling
Socket comm. and data processing
Thread 1
thread2
thread3
...
Thread n
Message
loop
Window procedure
Message handler #1
Message handler #2
Message handler #3
•••

18. Dialog based socket application (2/2)
Thread synchronization is needed
GUITCPclient.cpp
Application buffer ② ① ③ ④ ⑤
network
thread 1
thread 2