Tera Term Source Code Overview

1. Foreword
2. Skill Sets
3. Module Composition
4. Library Composition
5. Supporting Plug-in
6. Read and Write Configuration File
7. Secure Programming
8. Compatible with obsolete Windows
9. Debugging Method
10. Multithreading
11. DDE Communication
12. SSH Design and Implementation by TTSSH
13. Macro Language Design and Implementation
14. Caret Control
15. Serial Port
16. Binary Transfer Protocol

Foreword

Skill Sets

• MSDN library
• MSDN library(Japanese)

However, the CygTerm is built with the gcc compiler of the Cygwin package. So, the CygTerm program is implemented by using the gcc feature. The source code is the C language.

Module Composition

Library Composition

The "TTSSH" module uses the OpenSSL library to perform the cryptography processing. Is seems that the OpenSSL library has only the SSL(Secure Socket Layer) protocol function for web accessing, however that is wrong. The OpenSSL library supports basic cipher algorithm and the "TTSSH" module uses only basic function. In other words, the "TTSSH" module will not be almost affected when the OpenSSL library has the security hole.
The zlib library is used to compress the SSH packet. So, the packet compression is effective on lower network throughput like the dial-up connection, however the performance is not good on high-speed network. So, the packet compression function is disable by default.
The PuTTY is a terminal emulator for free, and defacto standard in world-wide. The Pageant program of the PuTTY package is the SSH authentication agent, and the TTSSH uses the PuTTY source code to support the Pageant authentication method.

Supporting Plug-in

• TTXModifyMenu()#ttplug.c -> TTProxy@TTXModifyMenu() -> TTSSH@TTXModifyMenu() -> TTX Kanji Menu@TTXModifyMenu()

static TTXExports Exports = {
/* This must contain the size of the structure. See below for its usage. */
	sizeof(TTXExports),

/* This is the load order number of this DLL. */
	ORDER,

/* Now we just list the functions that we've implemented. */
	TTXInit,
	NULL, /* TTXGetUIHooks */
	NULL, /* TTXGetSetupHooks */
	NULL, /* TTXOpenTCP */
	NULL, /* TTXCloseTCP */
	NULL, /* TTXSetWinSize */
	TTXModifyMenu,
	TTXModifyPopupMenu,
	TTXProcessCommand,
	NULL, /* TTXEnd */
	NULL  /* TTXSetCommandLine */
};

Read and Write Configuration File

	ts->ConfirmChangePaste =
		GetOnOff(Section, "ConfirmChangePaste", FName, TRUE);

	WriteOnOff(Section, "ConfirmChangePaste", FName,
		ts->ConfirmChangePaste);

Secure Programming

String Operation

• Security Enhancements in the CRT(MSDN Library)

Example of using the strncpy_s() function is below shown. The second argument(numberOfElements) is specified with the buffer size including the terminating null(\0). The writing buffer has only three bytes, five bytes data specified by the third argument(strSource) truncates to two bytes. As a result, the buf[] stores the "he\0" string.

char buf[3];
strncpy_s(buf, sizeof(buf), "hello", _TRUNCATE);

char str[7];
str[0] = '\0';
strncat_s(str, sizeof(str), "Tera", _TRUNCATE);
strncat_s(str, sizeof(str), "Term", _TRUNCATE);

char buf[3];
_snprintf_s(buf, sizeof(buf), _TRUNCATE, "abcdef");

Compatible with obsolete Windows

Dynamic Loading

static BOOL MySetLayeredWindowAttributes(HWND hwnd, COLORREF crKey, BYTE bAlpha, DWORD dwFlags)
{
	typedef BOOL (WINAPI *func)(HWND,COLORREF,BYTE,DWORD);
	static HMODULE g_hmodUser32 = NULL;
	static func g_pSetLayeredWindowAttributes = NULL;

	if (g_hmodUser32 == NULL) {
		g_hmodUser32 = LoadLibrary("user32.dll");
		if (g_hmodUser32 == NULL)
			return FALSE;

		g_pSetLayeredWindowAttributes =
			(func)GetProcAddress(g_hmodUser32, "SetLayeredWindowAttributes");
	}

	if (g_pSetLayeredWindowAttributes == NULL)
		return FALSE;

	return g_pSetLayeredWindowAttributes(hwnd, crKey, 
	                                     bAlpha, dwFlags);
}

Windows 95

Currently, Tera Term can work on the Windows 95 with a method despite Tera Term is built by the Visual Studio 2005. Certainly, this is Microsoft unofficial method.
The binary program built by the Visual Studio 2005 links the IsDebuggerPresent function by default. The program can not work on the Windows 95 with link error because the function is added from the Windows 98.
So, this problem can be avoided to define dummy symbol of the IsDebuggerPresent function on the Windows 95. For details, refer to the "comapt_w95.h" header.

• comapt_w95.h

Debugging Method

Debug printf

void OutputDebugPrintf(char *fmt, ...) {
	char tmp[1024];
	va_list arg;
	va_start(arg, fmt);
	_vsnprintf(tmp, sizeof(tmp), fmt, arg);
	OutputDebugString(tmp);
}

Memory leak

#ifdef _DEBUG
  _CrtSetDbgFlag(_CRTDBG_ALLOC_MEM_DF | _CRTDBG_LEAK_CHECK_DF);
#endif

Multithreading

#define WM_SEND_HEARTBEAT (WM_USER + 1)

static LRESULT CALLBACK telnet_heartbeat_dlg_proc(HWND hWnd, UINT msg, WPARAM wp, LPARAM lp)
{

	switch (msg) {
		case WM_INITDIALOG:
			return FALSE;

		case WM_SEND_HEARTBEAT:
			TelSendNOP();
			return TRUE;
			break;

		case WM_COMMAND:
			break;

		case WM_CLOSE:
			return TRUE;

		case WM_DESTROY:
			return TRUE;

		default:
			return FALSE;
	}
	return TRUE;
}

static unsigned _stdcall TelKeepAliveThread(void *dummy) {
  static int instance = 0;

  if (instance > 0)
    return 0;
  instance++;

  while (cv.Open && nop_interval > 0) {
    if (time(NULL) >= cv.LastSendTime + nop_interval) {
		SendMessage(keepalive_dialog, WM_SEND_HEARTBEAT, 0, 0);
    }

    Sleep(100);
  }
  instance--;
  return 0;
}

void TelStartKeepAliveThread() {
  unsigned tid;

  if (ts.TelKeepAliveInterval > 0) {
    nop_interval = ts.TelKeepAliveInterval;

	keepalive_dialog = CreateDialog(hInst, MAKEINTRESOURCE(IDD_BROADCAST_DIALOG),
               HVTWin, (DLGPROC)telnet_heartbeat_dlg_proc);

    keepalive_thread = (HANDLE)_beginthreadex(NULL, 0, TelKeepAliveThread, NULL, 0, &tid);
    if (keepalive_thread == (HANDLE)-1) {
      nop_interval = 0;
    }
  }
}

DDE Communication

Overview

• Dynamic Data Exchange(MSDN library)
• Dynamic Data Exchange Management Library(MSDN library)

Library

Implementation

	SetTopic();
	if (! InitDDE()) return;
	strncpy_s(Cmnd, sizeof(Cmnd),"TTPMACRO /D=", _TRUNCATE);
	strncat_s(Cmnd,sizeof(Cmnd),TopicName,_TRUNCATE);

  ConvH = DdeConnect(Inst, Service, Topic, NULL);
  if (ConvH == 0) return FALSE;
  Linked = TRUE;

  Cmd[0] = CmdSetHWnd;
  w = HIWORD(HWin);
  Word2HexStr(w,&(Cmd[1]));
  w = LOWORD(HWin);
  Word2HexStr(w,&(Cmd[5]));

  DdeClientTransaction(Cmd,strlen(Cmd)+1,ConvH,0,
    CF_OEMTEXT,XTYP_EXECUTE,1000,NULL);

  DdeClientTransaction(NULL,0,ConvH,Item,
    CF_OEMTEXT,XTYP_ADVSTART,1000,NULL);

Buffer Management

SSH Design and Implementation by TTSSH

Macro Language Design and Implementation

Caret Control

Serial Port

Overview

List up COM ports

	if (((h = GetModuleHandle("kernel32.dll")) != NULL) &&
	    (GetProcAddress(h, "QueryDosDeviceA") != NULL) &&
	    (QueryDosDevice(NULL, devicesBuff, 65535) != 0)) {
		p = devicesBuff;
		while (*p != '\0') {
			if (strncmp(p, "COM", 3) == 0 && p[3] != '\0') {
				ComPortTable[comports++] = atoi(p+3);
				if (comports >= ComPortMax)
					break;
			}
			p += (strlen(p)+1);
		}

Retrieve COM port full name

static void ListupSerialPort(LPWORD ComPortTable, int comports, char **ComPortDesc, int ComPortMax)
{
	GUID ClassGuid[1];
	DWORD dwRequiredSize;
	BOOL bRet;
	HDEVINFO DeviceInfoSet = NULL;
	SP_DEVINFO_DATA DeviceInfoData;
	DWORD dwMemberIndex = 0;
	int i;

	DeviceInfoData.cbSize = sizeof(SP_DEVINFO_DATA);

	bRet =
		SetupDiClassGuidsFromName(_T("PORTS"), (LPGUID) & ClassGuid, 1,
		                          &dwRequiredSize);
	if (!bRet) {
		goto cleanup;
	}

	DeviceInfoSet =
		SetupDiGetClassDevs(&ClassGuid[0], NULL, NULL, DIGCF_PRESENT | DIGCF_PROFILE);

	if (DeviceInfoSet) {
		dwMemberIndex = 0;
		while (SetupDiEnumDeviceInfo
		       (DeviceInfoSet, dwMemberIndex++, &DeviceInfoData)) {
			TCHAR szFriendlyName[MAX_PATH];
			TCHAR szPortName[MAX_PATH];
			DWORD dwReqSize = 0;
			DWORD dwPropType;
			DWORD dwType = REG_SZ;
			HKEY hKey = NULL;

			bRet = SetupDiGetDeviceRegistryProperty(DeviceInfoSet,
			                                        &DeviceInfoData,
			                                        SPDRP_FRIENDLYNAME,
			                                        &dwPropType,
			                                        (LPBYTE)
			                                        szFriendlyName,
			                                        sizeof(szFriendlyName),
			                                        &dwReqSize);

			hKey = SetupDiOpenDevRegKey(DeviceInfoSet,
			                            &DeviceInfoData,
			                            DICS_FLAG_GLOBAL,
			                            0, DIREG_DEV, KEY_READ);
			if (hKey) {
				long lRet;
				dwReqSize = sizeof(szPortName);
				lRet = RegQueryValueEx(hKey,
				                       _T("PortName"),
				                       0,
				                       &dwType,
				                       (LPBYTE) & szPortName,
				                       &dwReqSize);
				RegCloseKey(hKey);
			}

			if (_strnicmp(szPortName, "COM", 3) == 0) {  // Found COM port driver
				int port = atoi(&szPortName[3]);
				int i;

				for (i = 0 ; i < comports ; i++) {
					if (ComPortTable[i] == port) {  // Confirm COM connection
						ComPortDesc[i] = _strdup(szFriendlyName);
						break;
					}
				}
			}
		}
	}

cleanup:
	SetupDiDestroyDeviceInfoList(DeviceInfoSet);
}

Binary Transfer Protocol