Unit OS A: Windows Networking Unit OS A: Windows Networking

(1)

Unit OS A: Windows Networking Unit OS A: Windows Networking

A.3. A.3. Microsoft-specific extensions to Sockets Microsoft-specific extensions to Sockets and other Networking APIs

and other Networking APIs

(2)

Copyright Notice Copyright Notice

These materials are part of the

These materials are part of the Windows Operating Windows Operating System Internals Curriculum Development Kit,

System Internals Curriculum Development Kit, developed by David A. Solomon and Mark E.

developed by David A. Solomon and Mark E.

Russinovich with Andreas Polze Russinovich with Andreas Polze

Microsoft has licensed these materials from David Microsoft has licensed these materials from David Solomon Expert Seminars, Inc. for distribution to Solomon Expert Seminars, Inc. for distribution to academic organizations solely for use in academic academic organizations solely for use in academic environments (and not for commercial use)

environments (and not for commercial use)

(3)

Roadmap for Section A.3 Roadmap for Section A.3

Windows Sockets (winsock2) Extensions Windows Sockets (winsock2) Extensions

Web access APIs Web access APIs

Named pipes and mailslots Named pipes and mailslots

NetBIOS / Wnet API

(4)

Winsock 2.0 Features Winsock 2.0 Features

Windows NT 4.0 was the first operating system with native support Windows NT 4.0 was the first operating system with native support of the Winsock 2.0 specification:

of the Winsock 2.0 specification:

Access to protocols other than TCP/IP, Access to protocols other than TCP/IP, Overlapped I/O,

Overlapped I/O,

Ability to query and request specific qualities of service Ability to query and request specific qualities of service

New header file and libraries:

WS2_32.LIB / WS2_32.DLL WS2_32.LIB / WS2_32.DLL winsock2.h

winsock2.h

Microsoft extensions to Winsock have been moved out into their Microsoft extensions to Winsock have been moved out into their own separate DLL

own separate DLL

WINSOCK.DLL contains forwarders to these routines WINSOCK.DLL contains forwarders to these routines

(5)

Microsoft-specific Extensions Microsoft-specific Extensions

to Berkeley Sockets to Berkeley Sockets

Tailored to the message-passing environment of Tailored to the message-passing environment of windows

windows WSA –

WSA – Windows Sockets Asynchronous Windows Sockets Asynchronous prefix prefix Roots in Windows 3.1

Roots in Windows 3.1

Windows Sockets Committee Windows Sockets Committee

# include <winsock.h>

(6)

Request event notification for a Request event notification for a

socket socket

Request a message to the window hWnd whenever any of the network Request a message to the window hWnd whenever any of the network events specified by the lEvent occurs

events specified by the lEvent occurs. .

Message which should be sent is specified by the wMsg parameter.

The socket for which notification is required is identified by s The socket for which notification is required is identified by s

int PASCAL FAR WSAAsyncSelect ( SOCKET s, HWND hWnd,

unsigned int wMsg, long lEvent );

Value

Value MeaningMeaning FD_READ

FD_READ Want to receive notification of readiness for reading Want to receive notification of readiness for reading FD_WRITE

FD_WRITE Want to receive notification of readiness for writing Want to receive notification of readiness for writing FD_OOB

FD_OOB Want to receive notification of the arrival of out-of-band data Want to receive notification of the arrival of out-of-band data FD_ACCEPT

FD_ACCEPT Want to receive notification of incoming connections Want to receive notification of incoming connections FD_CONNECT

FD_CONNECT Want to receive notification of completed connection Want to receive notification of completed connection

(7)

WSAAsyncSelect (contd.) WSAAsyncSelect (contd.)

Every window must have a window procedure Every window must have a window procedure

Arguments to window procedure for notification window:

wParam contains socket number wParam contains socket number

lParam contains event code and any error that may have occured lParam contains event code and any error that may have occured Event status:

Event status:

LRESULT WINAPI WndProc( HWND hWnd,

UINT msg, WPARAM wParam, LPARAM lParam);

switch( msg ) {

case WM_PAINT: ...

case WM_DESTROY: ...

case FD_ACCEPT: ...

default: return( DefWindowProc( hWnd, msg, wParam, lParam ));

}

(8)

WSAAsynchSelect (contd.) WSAAsynchSelect (contd.)

Report the event:

WORD wEvent = WSAGETSELECTEVENT( lParam );

Enabling functions reactivate WSAAsyncSelect:

For FD_READ, FD_OOB events:

ReadFile(), read(), recv(), recvfrom() are enabling functions ReadFile(), read(), recv(), recvfrom() are enabling functions For FD_WRITE events:

For FD_WRITE events:

WriteFile(), write(), send(), sendto() are enabling functions WriteFile(), write(), send(), sendto() are enabling functions

Request notification of different events:

Call WSAAsyncSelect() again Call WSAAsyncSelect() again

(9)

WSAAsyncSelect (contd.) WSAAsyncSelect (contd.)

Issuing a WSAAsyncSelect() for a socket cancels any previous Issuing a WSAAsyncSelect() for a socket cancels any previous WSAAsyncSelect() for the same socket.

WSAAsyncSelect() for the same socket.

For example, to receive notification for both reading and writing, the For example, to receive notification for both reading and writing, the application must call WSAAsyncSelect() with both FD_READ and application must call WSAAsyncSelect() with both FD_READ and FD_WRITE, as follows:

FD_WRITE, as follows:

rc = WSAAsyncSelect(s, hWnd, wMsg, FD_READ | FD_WRITE);

It is not possible to specify different messages for different events.

The following code will not work; the second call will cancel the effects of the The following code will not work; the second call will cancel the effects of the first, and only FD_WRITE events will be reported with message wMsg2:

first, and only FD_WRITE events will be reported with message wMsg2:

rc = WSAAsyncSelect(s, hWnd, wMsg1, FD_READ);

rc = WSAAsyncSelect(s, hWnd, wMsg2, FD_WRITE);

To cancel all notification - i.e., to indicate that the Windows Sockets To cancel all notification - i.e., to indicate that the Windows Sockets

implementation should send no further messages related to network events on implementation should send no further messages related to network events on the socket - lEvent should be set to zero.

the socket - lEvent should be set to zero.

(10)

Use of WSAAsyncSelect Use of WSAAsyncSelect

- Server Side - Server Side

1.1. Create a socket and bind your address to itCreate a socket and bind your address to it

2.2. Call WSAAsyncSelect():Call WSAAsyncSelect():

Request FD_ACCEPT notification Request FD_ACCEPT notification

3.3. Call listen() – returns immediatelyCall listen() – returns immediately

4.4. When connection request comes in:When connection request comes in:

Notification window receives FD_ACCEPT notification Notification window receives FD_ACCEPT notification Respond by calling accept()

Respond by calling accept()

5.5. Call WSAAsyncSelect():Call WSAAsyncSelect():

Request FD_READ | FD_OOB | FD_CLOSE notifications for socket Request FD_READ | FD_OOB | FD_CLOSE notifications for socket returned by accept()

returned by accept()

6.6. Receiving FD_READ, FD_OOB notifications:Receiving FD_READ, FD_OOB notifications:

Call ReadFile(), read(), recv(), recvfrom() to retrieve the data Call ReadFile(), read(), recv(), recvfrom() to retrieve the data

7.7. Respond to FD_CLOSE notification by calling closesocket()Respond to FD_CLOSE notification by calling closesocket()

(11)

Use of WSAAsyncSelect() Use of WSAAsyncSelect()

- Client Side - Client Side

1. 1. Create a socket Create a socket

2. 2. Call WSAAsyncSelect(): Call WSAAsyncSelect():

Request FD_CONNECT notification Request FD_CONNECT notification

3. 3. Call connect() – returns immediately Call connect() – returns immediately

4. 4. When FD_CONNECT notification comes in: When FD_CONNECT notification comes in:

Request FD_READ | FD_OOB | FD_CLOSE notification on socket Request FD_READ | FD_OOB | FD_CLOSE notification on socket (reported in wParam)

(reported in wParam)

5. 5. When data from the server arrives: When data from the server arrives:

Notification window receives FD_READ or FD_OOB events Notification window receives FD_READ or FD_OOB events Respond by calling ReadFile(), read(), recv(), or recvfrom() Respond by calling ReadFile(), read(), recv(), or recvfrom() Client should be prepared for FD_CLOSE notification

Client should be prepared for FD_CLOSE notification

(12)

Get host information corresponding Get host information corresponding

to an address - asynchronous to an address - asynchronous

version version

type:

The type of the address, which must be The type of the address, which must be PF_INET.

PF_INET.

buf:

A pointer to the data area to receive the A pointer to the data area to receive the hostent data. Note that this must be larger hostent data. Note that this must be larger than the size of a hostent structure. It is than the size of a hostent structure. It is recommended that you supply a buffer of recommended that you supply a buffer of MAXGETHOSTSTRUCT bytes.

MAXGETHOSTSTRUCT bytes.

buflen:

The size of data area buf above.

• hWnd:

– The handle of the window which should receive a message when the asynchronous request completes.

• wMsg:

– The message to be received when the asynchronous request completes.

• addr:

– A pointer to the network address for the host. Host addresses are stored in network byte order.

• len:

– The length of the address, which must be 4 for PF_INET.

HANDLE PASCAL FAR WSAAsyncGetHostByAddr ( HWND hWnd, unsigned int wMsg,

const char FAR * addr, int len, int type, char FAR * buf, int buflen );

asynchronous version of gethostbyaddr()

(13)

WSAAsyncGetHostByAddr (contd.) WSAAsyncGetHostByAddr (contd.)

When the asynchronous operation is complete the application's When the asynchronous operation is complete the application's

window hWnd receives message wMsg.

The wParam argument contains the asynchronous task handle as The wParam argument contains the asynchronous task handle as

returned by the original function call.

The high 16 bits of lParam contain any error code.

The error code may be any error as defined in winsock.h.

An error code of zero indicates successful completion of the An error code of zero indicates successful completion of the

asynchronous operation.

On successful completion, the buffer supplied to the original function On successful completion, the buffer supplied to the original function

call contains a hostent structure.

To access the elements of this structure, the original buffer address To access the elements of this structure, the original buffer address

should be cast to a hostent structure pointer and accessed as should be cast to a hostent structure pointer and accessed as

appropriate.

(14)

Get host information corresponding Get host information corresponding

to a hostname - asynchronous to a hostname - asynchronous

version version

hWnd:

The handle of the window which should receive a message when the The handle of the window which should receive a message when the asynchronous request completes.

asynchronous request completes.

wMsg:

The message to be received when the asynchronous request completes.

Name:

A pointer to the name of the host.

Buf:Buf:

A pointer to the data area to receive the hostent data. It is recommended that you A pointer to the data area to receive the hostent data. It is recommended that you supply a buffer of MAXGETHOSTSTRUCT bytes.

supply a buffer of MAXGETHOSTSTRUCT bytes.

Buflen:

HANDLE PASCAL FAR WSAAsyncGetHostByName ( HWND hWnd, unsigned int wMsg,

const char FAR * name, char FAR * buf, int buflen );

asynchronous version of gethostbyname()

(15)

Get protocol information corresponding Get protocol information corresponding

to a protocol name - asynchronous to a protocol name - asynchronous

version version

hWnd hWnd

wMsg wMsg

name name

A pointer to the protocol name to be resolved.

buf buf

A pointer to the data area to receive the protoent data. (supply a buffer of A pointer to the data area to receive the protoent data. (supply a buffer of MAXGETHOSTSTRUCT bytes)

MAXGETHOSTSTRUCT bytes)

HANDLE PASCAL FAR WSAAsyncGetProtoByName ( HWND hWnd, unsigned int wMsg,

const char FAR * name, char FAR * buf, int buflen );

asynchronous version of getprotobyname()

(16)

Get protocol information corresponding Get protocol information corresponding

to a protocol number - asynchronous to a protocol number - asynchronous

version version

hWnd hWnd

wMsg wMsg

number number

The protocol number to be resolved, The protocol number to be resolved, in host byte order.

in host byte order.

buf buf

A pointer to the data area to receive the protoent data (supply a buffer of A pointer to the data area to receive the protoent data (supply a buffer of MAXGETHOSTSTRUCT bytes)

MAXGETHOSTSTRUCT bytes) buflen

buflen

HANDLE PASCAL FAR WSAAsyncGetProtoByNumber ( HWND hWnd, unsigned int wMsg,

int number, char FAR * buf, int buflen );

asynchronous version of getprotobynumber()

(17)

Additional Asynchronous Additional Asynchronous

Socket Routines Socket Routines

WSAAsyncGetServByName() WSAAsyncGetServByName() WSAAsyncGetServByPort() WSAAsyncGetServByPort() WSACancelAsyncRequest() WSACancelAsyncRequest() WSACancelBlockingCall() WSACancelBlockingCall() WSACleanup()

WSACleanup()

WSAGetLastError() WSAGetLastError() WSAIsBlocking() WSAIsBlocking()

WSASetBlockingHook(), WSAUnhookBlockingHook() WSASetBlockingHook(), WSAUnhookBlockingHook() WSASetLastError()

WSASetLastError() WSAStartup()

WSAStartup()

(18)

WSASetBlockingHook WSASetBlockingHook

Application invokes a blocking Sockets operation:

the Windows Sockets implementation initiates the operation and then the Windows Sockets implementation initiates the operation and then

enters a loop which is similar to the following pseudocode:

for(;;) { for(;;) {

/* flush messages for good user response */

while(BlockingHook()) ; while(BlockingHook()) ;

/* check for WSACancelBlockingCall() */

if(operation_cancelled()) break;

/* check to see if operation completed */

if(operation_complete()) break;

/* normal completion */

}}

support those applications which require more complex message processing –

MDI (multiple document

(19)

Web API: Internet Support Web API: Internet Support

WININET.DLL supports HTTP, FTP, Gopher protocols WININET.DLL supports HTTP, FTP, Gopher protocols General-purpose WinInet Functions

General-purpose WinInet Functions

InternetOpen InternetOpen

InternetConnect InternetConnect InternetOpenUrl InternetOpenUrl InternetReadFile InternetReadFile

InternetCloseHandle InternetCloseHandle

InternetSetStatusCallback InternetSetStatusCallback

InternetQueryOption InternetQueryOption

InternetSetOption

(20)

Internet Suport Internet Suport

(http/gopher protocols) (http/gopher protocols)

WinInet HTTP Functions WinInet HTTP Functions

HttpOpenRequest HttpOpenRequest

HttpAddRequestHeaders HttpAddRequestHeaders HttpSendRequest

HttpSendRequest HttpQueryInfo HttpQueryInfo

WinInet Gopher Functions WinInet Gopher Functions

GopherFindFirstFile GopherFindFirstFile GopherOpenFile GopherOpenFile

GopherCreateLocator GopherCreateLocator GopherGetAttribute GopherGetAttribute

(21)

Internet Support (ftp protocol) Internet Support (ftp protocol)

WinInet FTP Functions WinInet FTP Functions

FtpFindFirstFile FtpFindFirstFile

FtpGetFile FtpGetFile FtpPutFile FtpPutFile

FtpDeleteFile FtpDeleteFile

FtpRenameFile FtpRenameFile

FtpOpenFile FtpOpenFile

InternetWriteFile InternetWriteFile

FtpCreateDirectory FtpCreateDirectory

FtpRemoveDirectory FtpRemoveDirectory

FtpSetCurrentDirectory FtpSetCurrentDirectory FtpGetCurrentDirectory FtpGetCurrentDirectory

FtpCommand FtpCommand

InternetGetLastResponseInfo InternetGetLastResponseInfo

Most of the WinInet functions work with

or return HINTERNETs (handles to Internet).

While your code sees all HINTERNETs as the same type, one HINTERNET can mean

something completely different from another.

The first type of HINTERNET that you obtain comes when you initialize

WININET.DLL by calling InternetOpen.

This is the first of 13 possible subtypes of HINTERNETs.

(22)

HINTERNET subtypes HINTERNET subtypes

Query the subtype of Query the subtype of a particular handle a particular handle by calling:

by calling:

InternetQuery InternetQuery Option

Option

and sending it the and sending it the HINTERNET with the HINTERNET with the INTERNET_OPTION_H INTERNET_OPTION_H ANDLE_TYPE

ANDLE_TYPE parameter parameter

INTERNET_HANDLE_TYPE_INTERNET

INTERNET_HANDLE_TYPE_INTERNET 11 INTERNET_HANDLE_TYPE_CONNECT_FTP

INTERNET_HANDLE_TYPE_CONNECT_FTP 22 INTERNET_HANDLE_TYPE_CONNECT_GOPHER

INTERNET_HANDLE_TYPE_CONNECT_GOPHER 33 INTERNET_HANDLE_TYPE_CONNECT_HTTP

INTERNET_HANDLE_TYPE_CONNECT_HTTP 44 INTERNET_HANDLE_TYPE_FTP_FIND

INTERNET_HANDLE_TYPE_FTP_FIND 55 INTERNET_HANDLE_TYPE_FTP_FIND_HTML

INTERNET_HANDLE_TYPE_FTP_FIND_HTML 66 INTERNET_HANDLE_TYPE_FTP_FILE

INTERNET_HANDLE_TYPE_FTP_FILE 77 INTERNET_HANDLE_TYPE_FTP_FILE_HTML

INTERNET_HANDLE_TYPE_FTP_FILE_HTML 88 INTERNET_HANDLE_TYPE_GOPHER_FIND

INTERNET_HANDLE_TYPE_GOPHER_FIND 99 INTERNET_HANDLE_TYPE_GOPHER_FIND_HTML

INTERNET_HANDLE_TYPE_GOPHER_FIND_HTML 1010 INTERNET_HANDLE_TYPE_GOPHER_FILE

INTERNET_HANDLE_TYPE_GOPHER_FILE 1111 INTERNET_HANDLE_TYPE_GOPHER_FILE_HTML

INTERNET_HANDLE_TYPE_GOPHER_FILE_HTML 1212 INTERNET_HANDLE_TYPE_HTTP_REQUEST

INTERNET_HANDLE_TYPE_HTTP_REQUEST 1313

(23)

Windows HTTP Services

Windows HTTP Services (WinHTTP) (WinHTTP)

HTTP client API to send requests through the HTTP HTTP client API to send requests through the HTTP protocol to other HTTP servers

protocol to other HTTP servers

WinHTTP supports desktop client applications, Windows WinHTTP supports desktop client applications, Windows

services, and Windows server-based applications services, and Windows server-based applications

WinHTTP offers both a C/C++ application programming WinHTTP offers both a C/C++ application programming

interface (API) and a COM automation component use in interface (API) and a COM automation component use in

Active Server Pages Active Server Pages

WinHTTP 5.1 is an OS component of:

Windows Server 2003 family Windows Server 2003 family

Windows XP SP1 Windows XP SP1

Windows 2000 SP3 (except Datacenter Server)

(24)

Usage of the WinHTTP API Usage of the WinHTTP API

Windows HTTP API exposes a set of C/C++ functions that enable Windows HTTP API exposes a set of C/C++ functions that enable applications to access HTTP resources on the Web

applications to access HTTP resources on the Web

(25)

Using Internet Functions Using Internet Functions

After setting up WININET.DLL, the initial HINTERNET is usually passed to After setting up WININET.DLL, the initial HINTERNET is usually passed to InternetConnect,

InternetConnect,

parameter indicates the type of connecting server (HTTP, FTP, or parameter indicates the type of connecting server (HTTP, FTP, or Gopher).

Gopher).

InternetConnect returns another subtype of HINTERNET, which is then InternetConnect returns another subtype of HINTERNET, which is then passed to the appropriate HTTP, FTP, or Gopher functions.

passed to the appropriate HTTP, FTP, or Gopher functions.

Alternatively call InternetOpenUrl (parses the URL; connects to the Alternatively call InternetOpenUrl (parses the URL; connects to the appropriate type of server automatically)

appropriate type of server automatically) After connecting to the desired server:

After connecting to the desired server:

turn to the protocol-specific functions turn to the protocol-specific functions

read data from the server via InternetReadFile (works with read data from the server via InternetReadFile (works with HINTERNETs for any of the three supported protocols) HINTERNETs for any of the three supported protocols) Before exiting the program:

Before exiting the program:

all of the HINTERNETs should be closed by calling all of the HINTERNETs should be closed by calling InternetCloseHandle.

InternetCloseHandle.

(26)

Named Pipes Named Pipes

Message oriented:

Reading process can read varying-length messages precisely as Reading process can read varying-length messages precisely as sent by the writing process

sent by the writing process

Bi-directional Bi-directional

Two processes can exchange messages over the same pipe Two processes can exchange messages over the same pipe

Multiple, independent instances of a named pipe:

Several clients can communicate with a single server Several clients can communicate with a single server using the same instance

using the same instance

Server can respond to client using the same instance Server can respond to client using the same instance

Pipe can be accessed over the network Pipe can be accessed over the network

location transparency location transparency

Convenience and connection functions

(27)

Using Named Pipes Using Named Pipes

lpszPipeName:

lpszPipeName: \\.\pipe\[\\.\pipe\[path]pipenamepath]pipename

Not possible to create a pipe on remote machine (. – local machine) Not possible to create a pipe on remote machine (. – local machine) fdwOpenMode:

fdwOpenMode:

PIPE_ACCESS_DUPLEX, PIPE_ACCESS_INBOUND, PIPE_ACCESS_DUPLEX, PIPE_ACCESS_INBOUND, PIPE_ACCESS_OUTBOUND

PIPE_ACCESS_OUTBOUND fdwPipeMode:

fdwPipeMode:

PIPE_TYPE_BYTE or PIPE_TYPE_MESSAGE PIPE_TYPE_BYTE or PIPE_TYPE_MESSAGE

PIPE_READMODE_BYTE or PIPE_READMODE_MESSAGE PIPE_READMODE_BYTE or PIPE_READMODE_MESSAGE PIPE_WAIT or PIPE_NOWAIT (will ReadFile block?)

PIPE_WAIT or PIPE_NOWAIT (will ReadFile block?)

HANDLE CreateNamedPipe (LPCTSTR lpszPipeName, DWORD fdwOpenMode, DWORD fdwPipMode DWORD nMaxInstances, DWORD cbOutBuf, DWORD cbInBuf, DWORD dwTimeOut,

LPSECURITY_ATTRIBUTES lpsa );

Use same flag settings for all instances of a named pipe

(28)

Named Pipes (contd.) Named Pipes (contd.)

nMaxInstances:

Number of instances, Number of instances,

PIPE_UNLIMITED_INSTANCES: OS choice based on resources PIPE_UNLIMITED_INSTANCES: OS choice based on resources dwTimeOut

dwTimeOut

Default time-out period (in msec) for WaitNamedPipe() Default time-out period (in msec) for WaitNamedPipe() First CreateNamedPipe creates named pipe

First CreateNamedPipe creates named pipe

Closing handle to last instance deletes named pipe Closing handle to last instance deletes named pipe Polling a pipe:

Polling a pipe:

Nondestructive – is there a message waiting for ReadFile Nondestructive – is there a message waiting for ReadFile

BOOL PeekNamedPipe (HANDLE hPipe,

LPVOID lpvBuffer, DWORD cbBuffer,

LPDWORD lpcbRead, LPDWORD lpcbAvail, LPDWORD lpcbMessage);

(29)

Named Pipe Client Connections Named Pipe Client Connections

CreateFile with named pipe name:

\\.\pipe\[

\\.\pipe\[path]pipenamepath]pipename

\\\\servername\pipe\[path]pipenameservername\pipe\[path]pipename

First method gives better performance (local server) First method gives better performance (local server)

Status Functions:

GetNamedPipeHandleState GetNamedPipeHandleState SetNamedPipeHandleState SetNamedPipeHandleState GetNamedPipeInfo

GetNamedPipeInfo

(30)

Convenience Functions Convenience Functions

WriteFile / ReadFile sequence:

BOOL TransactNamedPipe( HANDLE hNamedPipe, LPVOID lpvWriteBuf, DWORD cbWriteBuf, LPVOID lpvReadBuf, DWORD cbReadBuf, LPDOWRD lpcbRead, LPOVERLAPPED lpa);

• CreateFile / WriteFile / ReadFile / CloseHandle:

- dwTimeOut: NMPWAIT_NOWAIT, NMPWAIT_WIAT_FOREVER, NMPWAIT_USE_DEFAULT_WAIT

BOOL CallNamedPipe( LPCTSTR lpszPipeName, LPVOID lpvWriteBuf, DWORD cbWriteBuf, LPVOID lpvReadBuf, DWORD cbReadBuf, LPDWORD lpcbRead, DWORD dwTimeOut);

(31)

Server: eliminate the polling loop Server: eliminate the polling loop

lpo == NULL:

Call will return as soon as there is a client connection Call will return as soon as there is a client connection

Returns false if client connected between CreateNamed Pipe call Returns false if client connected between CreateNamed Pipe call and ConnectNamedPipe()

and ConnectNamedPipe()

Use DisconnectNamedPipe to free the handle for connection from another Use DisconnectNamedPipe to free the handle for connection from another client

client

WaitNamedPipe():

Client may wait for server‘s ConnectNamedPipe() Client may wait for server‘s ConnectNamedPipe()

Security rights for named pipes:

GENERIC_READ, GENERIC_WRITE, SYNCHRONIZE GENERIC_READ, GENERIC_WRITE, SYNCHRONIZE

BOOL ConnectNamedPipe (HANDLE hNamedPipe, LPOVERLAPPED lpo );

(32)

Windows IPC - Mailslots Windows IPC - Mailslots

Broadcast mechanism:

One-directional One-directional

Mutliple writers/multiple readers (frequently: one-to-many comm.) Mutliple writers/multiple readers (frequently: one-to-many comm.) Message delivery is unreliable

Message delivery is unreliable

Can be located over a network domain Can be located over a network domain

Message lengths are limited (w2k: < 426 byte) Message lengths are limited (w2k: < 426 byte) Operations on the mailslot:

Operations on the mailslot:

Each reader (server) creates mailslot with CreateMailslot() Each reader (server) creates mailslot with CreateMailslot() Write-only client opens mailslot with CreateFile() and

Write-only client opens mailslot with CreateFile() and

uses WriteFile() – open will fail if there are no waiting readers uses WriteFile() – open will fail if there are no waiting readers Client‘s message can be read by all servers (readers)

Client‘s message can be read by all servers (readers) Client lookup:

Client lookup: \\*\mailslot\mailslotname\\*\mailslot\mailslotname

Client will connect to every server in network domain Client will connect to every server in network domain

Mailslots bear some nasty implementation details;

they are almost never used

(33)

Locate a server via mailslot Locate a server via mailslot

hMS = CreateMailslot(

“\\.\mailslot\status“);

ReadFile(hMS, &ServStat);

/* connect to server */

hMS = CreateMailslot(

ReadFile(hMS, &ServStat);

/* connect to server */

App client 0

App client n

Mailslot Servers

While (...) { Sleep(...);

hMS = CreateFile(

...

WriteFile(hMS, &StatInfo }

App Server

Mailslot Client

Message is sent periodically

(34)

Creating a mailslot Creating a mailslot

lpszName points to a name of the form lpszName points to a name of the form

\\.\mailslot\[path]name

Name must be unique; mailslot is created locally Name must be unique; mailslot is created locally

cbMaxMsg is msg size in byte cbMaxMsg is msg size in byte dwReadTimeout

dwReadTimeout

Read operation will wait for so many msec Read operation will wait for so many msec 0 – immediate return

0 – immediate return

MAILSLOT_WAIT_FOREVER – infinite wait MAILSLOT_WAIT_FOREVER – infinite wait

HANDLE CreateMailslot(LPCTSTR lpszName, DWORD cbMaxMsg,

DWORD dwReadTimeout,

LPSECURITY_ATTRIBUTES lpsa);

(35)

Opening a mailslot Opening a mailslot

CreateFile with the following names:

\\.\mailslot\[path]name

\\.\mailslot\[path]name - retrieve handle for local mailslot - retrieve handle for local mailslot

\\host\mailslot\[path]name

\\host\mailslot\[path]name - retrieve handle - retrieve handle for mailslot on specified host

for mailslot on specified host

\\domain\mailslot\[path]name

\\domain\mailslot\[path]name - returns handle representing all - returns handle representing all mailslots on machines in the domain

mailslots on machines in the domain

\\*\mailslot\[path]name

\\*\mailslot\[path]name - returns handle representing mailslots on - returns handle representing mailslots on machines in the system‘s primary domain: max mesg. len: 400 bytes machines in the system‘s primary domain: max mesg. len: 400 bytes Client must specifiy FILE_SHARE_READ flag

Client must specifiy FILE_SHARE_READ flag

GetMailslotInfo() and SetMailslotInfo() are similar to their named GetMailslotInfo() and SetMailslotInfo() are similar to their named pipe counterparts

pipe counterparts

(36)

W W N N et API et API

Connection Functions Connection Functions

WNetAddConnection WNetAddConnection WNetAddConnection2 WNetAddConnection2 WNetAddConnection3 WNetAddConnection3 WNetCancelConnection WNetCancelConnection WNetCancelConnection2 WNetCancelConnection2 WNetConnectionDialog WNetConnectionDialog WNetConnectionDialog1 WNetConnectionDialog1 WNetDisconnectDialog WNetDisconnectDialog WNetDisconnectDialog1 WNetDisconnectDialog1 WNetGetConnection WNetGetConnection WNetGetUniversalName WNetGetUniversalName

• Enumeration Functions

– WNetCloseEnum – WNetEnumResource – WNetOpenEnum

• Information Functions

– WNetGetNetworkInformation – WNetGetLastError

– WNetGetProviderName

– WNetGetResourceInformation – WNetGetResourceParent

• User Functions

– WNetGetUser

(37)

WNetAddConnection WNetAddConnection

connect a local device to a network resource connect a local device to a network resource successful connection is persistent

successful connection is persistent

system automatically restores the connection during subsequent logon operations system automatically restores the connection during subsequent logon operations lpRemoteName

lpRemoteName

Points to a null-terminated string that specifies the network resource to connect to.

lpPassword lpPassword

Points to a null-terminated string that specifies the password to be used to make a connection. This Points to a null-terminated string that specifies the password to be used to make a connection. This parameter is usually the password associated with the current user.

parameter is usually the password associated with the current user.

NULL: the default password is used. If the string is empty, no password is used.

lpLocalName lpLocalName

Points to a null-terminated string that specifies the name of a local device to be redirected, such as F:

or LPT1. The case of the characters in the string is not important.

DWORD WNetAddConnection(

LPTSTR lpRemoteName, // pointer to network device name LPTSTR lpPassword, // pointer to password

LPTSTR lpLocalName // pointer to local device name );

(38)

WNetGetConnection WNetGetConnection

retrieves the name of the network resource associated with a local device.

DWORD WNetGetConnection(

LPCTSTR lpLocalName, // pointer to local name

LPTSTR lpRemoteName, // pointer to buffer for remote name LPDWORD lpnLength // pointer to buffer size, in characters );

• lpLocalName

• Points to a null-terminated string that specifies the name of the local device to get the network name for.

• lpRemoteName

• Points to a buffer that receives the null-terminated remote name

• lpnLength

• Points to a variable that specifies the size´of the buffer.

(39)