Silverlight utility tip series: 67. socket communication under Silverlight

For communication in Silverlight, data transmission can only be performed on ports between and, in addition, the Silverlight client automatically sends a "<policy-file-Request/>" Statement request to the server on port 943, then, port 943 on the server sends back the following files to permit socket communication.

<? XML version = "  1.0  " Encoding = "  UTF-8  " ?> <Access-Policy> <cross-domain-access> <Policy> <allow- From > <Domain uri = "  *  " /> </Allow- From > <Grant-to> <socket-resource Port = "  4502-4534  " Protocol = "  TCP  " /> </Grant-to> </Policy> </Cross-Domain-access> </access-Policy>

A. Now let's first look at the server sideCode, Mainly divided into policy response steps and service response steps.

Step 1: Enable listening to port 943 for security policy file requests

Step 2: If the client request is <policy-file-Request/>, the security policy file is sent to the client as bytes.

Service Step 1: Start the server and listen to port 4525. Is there a socket conversation request?

Step 2: If there is a connection requested by the client, send a message to inform the client

The Code is as follows:

    Class  Program {  Static   Void Main ( String  [] ARGs ){  //  Policy Step 1: Start listening to port 943 to check whether security policy file requests are required Thread access = New Thread ( New  Threadstart (accessthread); Access. Start ();  //  Service Step 1: Start the server and listen to port 4525. Is there a socket conversation request? Thread Server = New Thread ( New  Threadstart (serverthread); server. Start ();}  //  Policy request listener          Static   Void  Accessthread (){  //  Obtain the socket server for port 943 listening Socket socket = getsocketserver ( 943  );  While (True  ) {Socket new_access = Socket. Accept ();  String Clientpolicystring = "  <Policy-file-Request/>  "  ;  Byte [] Requestbytes = New   Byte  [Clientpolicystring. Length]; new_access.receive (requestbytes );  String Requeststring = system. Text. encoding. utf8.getstring (requestbytes, 0  , Requestbytes. Length );  If (Requeststring = Clientpolicystring ){  //  Policy Step 2: If the client request is <policy-file-Request/>, the security policy file is sent to the client as bytes.                      Byte [] Accpolicytes = Getpolicytoclient (); new_access.send (accessbytes, accessbytes. length, socketflags. None); new_access.close ();} thread. Sleep (  100 );}}  Static   Void  Serverthread (){  //  Obtain the socket server for port 4525 listening Socket socket = getsocketserver ( 4525  );  While ( True  ) {Socket _ socket = Socket. Accept ();  // Service Step 2: If a client requests a connection, send a message to inform the client                  Byte [] B2 = New   Byte [ 1024  ]; _ Socket. Receive (B2); console. writeline (encoding. utf8.getstring (B2). Replace (  "  \ 0  " , ""  ));  String Recstring = "  I have received the message. "  ; _ Socket. Send (encoding. utf8.getbytes (recstring); _ socket. Close (); thread. Sleep (  100  );}}  //  Establish a socket server based on the port          Static Socket getsocketserver ( Int  SERVERPORT) {Socket socket = New  Socket (addressfamily. InterNetwork, sockettype. Stream, protocoltype. TCP); socket. BIND ( New  Ipendpoint (IPaddress. Any, SERVERPORT); socket. Listen (  40  );  Return  Socket ;}  //  Obtain the byte of the security policy file []          Static   Byte  [] Getpolicytoclient (){  String Path = environment. currentdirectory. Replace ( "  \ Bin \ debug " , ""  ); Filestream FS = New Filestream (path + @"  \ Clientaccesspolicy. xml  "  , Filemode. Open );  Int Length = ( Int  ) Fs. length;  Byte [] Bytes = New   Byte [Length]; FS. Read (bytes,  0  , Length); FS. Close ();  Return  Bytes ;}} 

B. Next, let's look at the client operations in the following steps:

Client Step 1: Initiate a server connection request.

Step 2: The connection to the server is successful. Put the data to be sent into the buffer zone and send a message request to the server asynchronously.

Client step 3: The message is successfully sent. In this case, a new buffer instance is set and a message is asynchronously received from the server.

Client Step 4: Gets the message returned by the server and closes the socket.

The client CS code is as follows:

     Public   Partial   Class  Mainpage: usercontrol { Public  Mainpage () {initializecomponent ();} system. net. sockets. Socket socket;  Private   Void Button#click ( Object  Sender, routedeventargs e ){  Byte [] Userbytes = encoding. utf8.getbytes ( This  . Tbinput. Text); socket = New System. net. sockets. socket (addressfamily. InterNetwork, sockettype. Stream, protocoltype. TCP); socketasynceventargs socketargs = New  Socketasynceventargs (); socketargs. remoteendpoint = New Dnsendpoint ( "  127.0.0.1  " , 4525  );  //  Convert the content to byte [] and save it to the usertoken attribute. Socketargs. usertoken =Userbytes; socketargs. Completed + = New Eventhandler <socketasynceventargs> (Socketargs_completed );  //  Client Step 1: Initiate a server connection request.  Socket. connectasync (socketargs );}  //  This method is activated for each socket operation, including connect/send/receive/none)          Void Socketargs_completed ( Object  Sender, socketasynceventargs e ){ If (E. lastoperation = Socketasyncoperation. Connect ){  //  Client Step 2: connect to the server successfully, put the data to be sent into the buffer, and then asynchronously send a message request to the server                  Byte [] Userbytes = ( Byte  []) E. usertoken; E. setbuffer (userbytes,  0  , Userbytes. Length); socket. sendasync (E );}  Else   If (E. lastoperation =Socketasyncoperation. Send ){  //  Client Step 3: the message is successfully sent. In this case, a new buffer instance is set and the server asynchronously receives the message returned by the server.                  Byte [] Userbytes = New   Byte [ 1024  ]; E. setbuffer (userbytes,  0  , Userbytes. Length); socket. receiveasync (E );}  Else   If (E. lastoperation =Socketasyncoperation. Receive ){  //  Client Step 4: get the message returned by the server and disable socket                  String Receviestr = encoding. utf8.getstring (E. buffer, 0 , E. Buffer. Length). Replace ( "  \ 0  " , ""  );  //  Because it is an asynchronous socket request, you need to use the UI thread to update the Display Effect of lbshowmessage.                  This . Lbshowmessage. Dispatcher. begininvoke ( New  Dothingdele (dothing), receviestr); socket. Close ();}}  //  Update the UI          Public   Void Dothing ( String  Arg ){  This . Lbshowmessage. content = This . Lbshowmessage. content + "  ->  " +ARG ;}  //  A declared dothing method delegate          Public   Delegate   Void Dothingdele ( String  Arg );} 

The front-end code of the client's XAML is as follows:

<Grid X: Name = "  Layoutroot  " Background = "  White  " Showgridlines ="  True  " > <Textbox Height = "  23  " Horizontalalignment = "  Left  " Margin = "  20, 20, 0, 0  "  Name = "  Tbinput  " Verticalalignment = "  Top  " Width = "  243  " /> <Button content = "  Send  " Height = "  23  " Horizontalalignment = "  Left  " Margin = "  279,20, 0, 0  " Name = "  Button1  " Verticalalignment = "  Top  "  Width = "  75  " Click = " Button#click  " /> <SDK: Label Height = "  28  " Horizontalalignment = "  Left  " Margin = "  20, 57, 0, 0  "  Name = "  Lbshowmessage  " Verticalalignment ="  Top  " Width = "  358  " /> </GRID>

The final effect is as follows. If you need the source code, click slsocket.zip to download it. This article demonstrates the simplest communication effect: