multi-threaded client-server socket class - the code project - internet & network.mht

多线程通信

            src=3D"http://www.codeproject.com/script/images/t.gif" =
width=3D160> </TD>
          <TD width=3D"100%">
            <TABLE class=3DSearchHeaderBar cellSpacing=3D0 =
width=3D"100%">
              <TBODY>
              <TR>
                <TD vAlign=3Dcenter noWrap align=3Dright width=3D"60%">
                  <FORM style=3D"MARGIN: 0px" name=3DSearch =
action=3D/info/search.asp=20
                  method=3Dpost><B>Search &nbsp;</B><INPUT =
class=3DsmallText=20
                  style=3D"WIDTH: 200px" name=3Dtarget> <SELECT=20
                  style=3D"FONT-WEIGHT: bold; FONT-SIZE: 8pt" name=3Dst> =
<OPTION=20
                    value=3Dkw selected>Articles</OPTION> <OPTION=20
                    value=3Dau>Authors</OPTION></SELECT> <INPUT =
style=3D"FONT-WEIGHT: bold; FONT-SIZE: 8pt" type=3Dsubmit value=3D" Go! =
">=20
                  &nbsp; </FORM></TD>
                <TD class=3DtinyText noWrap><A=20
                  =
href=3D"http://www.codeproject.com/info/search.asp">Advanced=20
                  Search</A><BR><A=20
                  =
href=3D"http://www.codeproject.com/script/articles/sections.asp">Sitemap<=
/A>=20
                </TD></TR></TBODY></TABLE>
            <TABLE width=3D"100%">
              <TBODY>
              <TR vAlign=3Dtop>
                <TD class=3DSmallText noWrap>
                  <TABLE>
                    <TBODY>
                    <TR>
                      <TD class=3DsmallText noWrap><IMG=20
                        =
src=3D"http://www.codeproject.com/images/print.gif"=20
                        align=3DabsMiddle> <A=20
                        =
href=3D"http://www.codeproject.com/internet/serversocket.asp?print=3Dtrue=
"=20
                        target=3D_print>Print</A></TD>
                      <TD class=3DsmallText noWrap><IMG=20
                        =
src=3D"http://www.codeproject.com/script/images/sitebuild_icon.gif"=20
                        align=3DabsMiddle><A=20
                        =
href=3D"http://www.codeproject.com/script/submit/ReportProblem.asp?GUID=3D=
ServerSocket%2Finternet6%2F23%2F2002">Broken=20
                        Article?</A></TD>
                      <TD class=3DsmallText noWrap><IMG=20
                        =
src=3D"http://www.codeproject.com/images/link.gif"=20
                        align=3DabsMiddle><A=20
                        =
href=3D"http://www.codeproject.com/script/profile/add_bookmark.asp?t=3D0&=
amp;ct=3D%2Finternet%2Fserversocket%2Easp&amp;guid=3DServerSocket%2Finter=
net6%2F23%2F2002">Bookmark</A></TD>
                      <TD class=3DsmallText noWrap><IMG=20
                        =
src=3D"http://www.codeproject.com/images/mail_small.gif"=20
                        align=3DabsMiddle> <A=20
                        =
href=3D"http://www.codeproject.com/internet/serversocket.asp#__comments">=
Discuss</A></TD>
                      <TD class=3DsmallText noWrap><IMG=20
                        =
src=3D"http://www.codeproject.com/images/mail.gif"=20
                        align=3DabsMiddle> <A=20
                        =
href=3D"http://www.codeproject.com/script/recommend/form.asp?guid=3DServe=
rSocket%2Finternet6%2F23%2F2002">Send=20
                        to a friend</A></TD></TR></TBODY></TABLE></TD>
                <TD noWrap align=3Dright><A name=3D__top></A>
                  <TABLE>
                    <TBODY>
                    <TR>
                      <TD class=3DsmallText align=3Dright>127 votes for =
this=20
                        article.</TD>
                      <TD>
                        <TABLE cellSpacing=3D0 cellPadding=3D0 =
border=3D2>
                          <TBODY>
                          <TR>
                            <TD><IMG height=3D5=20
                              =
src=3D"http://www.codeproject.com/script/images/red.gif"=20
                              width=3D20 border=3D0></TD>
                            <TD><IMG height=3D5=20
                              =
src=3D"http://www.codeproject.com/script/images/red.gif"=20
                              width=3D20 border=3D0></TD>
                            <TD><IMG height=3D5=20
                              =
src=3D"http://www.codeproject.com/script/images/red.gif"=20
                              width=3D20 border=3D0></TD>
                            <TD><IMG height=3D5=20
                              =
src=3D"http://www.codeproject.com/script/images/red.gif"=20
                              width=3D20 border=3D0></TD>
                            <TD><IMG height=3D5=20
                              =
src=3D"http://www.codeproject.com/script/images/red.gif"=20
                              width=3D7 border=3D0><IMG height=3D5=20
                              =
src=3D"http://www.codeproject.com/script/images/white.gif"=20
                              width=3D13 =
border=3D0></TD></TR></TBODY></TABLE></TD></TR>
                    <TR>
                      <TD class=3DsmallText align=3Dright colSpan=3D2><A =

                        title=3D"Calculated as rating x Log10(# votes)"=20
                        =
href=3D"http://www.codeproject.com/script/articles/top_articles.asp?st=3D=
2">Popularity:=20
                        9.18</A>. Rating: <B>4.36</B> out of=20
                  =
5.</TD></TR></TBODY></TABLE></TD></TR></TBODY></TABLE></TD></TR>
        <TR>
          <TD class=3DArticlePane><SPAN id=3DintelliTXT>
            <DIV id=3Dcontentdiv><!-- Article Starts -->
            <UL class=3Ddownload>
              <LI><A=20
              =
href=3D"http://www.codeproject.com/internet/ServerSocket/ServerSocket_dem=
o.zip">Download=20
              ServerSocket demo project -&nbsp;47.3 Kb</A> </LI></UL>
            <H2>Screenshots</H2>
            <P><B>Note:</B> The demo can be started in Client or Server =
mode,=20
            execute with "/C" (or "/CLIENT") or "/S" (or "/SERVER", this =
is the=20
            default).</P>
            <P><IMG height=3D284 alt=3D"Server Socket App - Screenshot"=20
            =
src=3D"http://www.codeproject.com/internet/ServerSocket/serversocket.gif"=
=20
            width=3D350></P>
            <P><IMG height=3D284 alt=3D"Client Socket App - Screenshot"=20
            =
src=3D"http://www.codeproject.com/internet/ServerSocket/clientsocket.gif"=
=20
            width=3D350></P>
            <H2>Introduction</H2>
            <P>This article is about a client/server multi-threaded =
socket=20
            class. The thread is optional since the developer/designer =
is still=20
            responsible to decide if he/she needs it. There are other =
Socket=20
            classes here and other places over the Internet but none of =
them can=20
            provide feedback (event detection) to your application like =
this one=20
            does. It provides you with the following events detection:=20
            connection established, connection dropped, connection =
failed and=20
            data reception (including 0 byte packet).</P>
            <H2>Description</H2>
            <P>This article presents a new socket class which supports =
both TCP=20
            and UDP communication. But it provides some advantages =
compared to=20
            other classes that you may find here or on some other Socket =

            Programming articles. First of all, this class doesn't have =
any=20
            limitation like the need to provide a window handle to be =
used. This=20
            limitation is bad if all you want is a simple console =
application.=20
            So this library doesn't have such a limitation. It also =
provides=20
            threading support automatically for you, which handles the =
socket=20
            connection and disconnection to a peer. It also features =
some=20
            options not yet found in any socket classes that I have seen =
so far.=20
            It supports both client and server sockets. A server socket =
can be=20
            referred as to a socket that can accept many connections. =
And a=20
            client socket is a socket that is connected to server =
socket. You=20
            may still use this class to communicate between two =
applications=20
            without establishing a connection. In the latter case, you =
will want=20
            to create two UDP server sockets (one for each application). =
This=20
            class also helps reduce coding need to create chat-like =
applications=20
            and IPC (Inter-Process Communication) between two or more=20
            applications (processes). Reliable communication between two =
peers=20
            is also supported with TCP/IP with error handling. You may =
want to=20
            use the smart addressing operation to control the =
destination of the=20
            data being transmitted (UDP only). TCP operation of this =
class deals=20
            only with communication between two peers.</P>
            <P>Now for those not familiar with IP Socket, the following =
section=20
            will give some details on how it works. This is also the =
goal with=20
            this article: explain the basic functionality behind socket=20
            objects.</P>
            <H3>TCP/IP stack</H3>
            <P>The TCP/IP stack is shorter than the OSI one:</P>
            <P><IMG height=3D328=20
            =
src=3D"http://www.codeproject.com/internet/ServerSocket/tcp_stack.gif"=20
            width=3D437></P>
            <P>TCP is a connection-oriented protocol, UDP (User Datagram =

            Protocol) is a connectionless protocol.</P>
            <H3>IP datagrams</H3>
            <P>The IP layer provides a connectionless and unreliable =
delivery=20
            system. It considers each datagram independently of the =
others. Any=20
            association between datagrams must be supplied by the higher =
layers.=20
            The IP layer supplies a checksum that includes its own =
header. The=20
            header includes the source and destination addresses. The IP =
layer=20
            handles routing through an Internet. It is also responsible =
for=20
            breaking up large datagrams into smaller ones for =
transmission and=20
            reassembling them at the other end.</P>
            <H3>UDP</H3>
            <P>UDP is also connectionless and unreliable. What it adds =
to IP is=20
            a checksum for the contents of the datagram and port =
numbers. These=20
            are used to give a client/server model - see later.</P>
            <H3>TCP</H3>
            <P>TCP supplies logic to give a reliable connection-oriented =

            protocol above IP. It provides a virtual circuit that two =
processes=20
            can use to communicate.</P>
            <H3>Internet addresses</H3>
            <P>In order to use a service, you must be able to find it. =
The=20
            Internet uses an address scheme for machines so that they =
can be=20
            located. The address is a 32 bit integer which gives the IP =
address.=20
            This encodes a network ID and more addressing. The network =
ID falls=20
            into various classes according to the size of the network=20
            address.</P>
            <H3>Network address</H3>
            <P>Class A uses 8 bits for the network address with 24 bits =
left=20
            over for other addressing. Class B uses 16 bit network =
addressing.=20
            Class C uses 24 bit network addressing and class D uses all =
32.</P>
            <H3>Subnet address</H3>
            <P>Internally, the Unix network is divided into subnetworks. =

            Building 11 is currently on one subnetwork and uses 10-bit=20
            addressing, allowing 1024 different hosts.</P>
            <H3>Host address</H3>
            <P>8 bits are finally used for host addresses within our =
subnet.=20
            This places a limit of 256 machines that can be on the =
subnet.</P>
            <H3>Total address</H3>
            <P><IMG height=3D145=20
            =
src=3D"http://www.codeproject.com/internet/ServerSocket/inet_addr.gif"=20
            width=3D330></P>
            <P>The 32 bit address is usually written as 4 integers =
separated by=20
            dots.</P>
            <H3>Port addresses</H3>
            <P>A service exists on a host, and is identified by its =
port. This=20
            is a 16 bit number. To send a message to a server, you send =
it to=20
            the port for that service of the host that it is running on. =
This is=20
            not location transparency! Certain of these ports are "well=20
            known".</P>
            <P>For example,</P>
            <TABLE cols=3D3 width=3D400 border=3D0>
              <TBODY>
              <TR>
                <TD width=3D"40%">tcpmux</TD>
                <TD width=3D"20%">1</TD>
                <TD width=3D"40%">TCP</TD></TR>
              <TR>
                <TD width=3D"40%">echo</TD>
                <TD width=3D"20%">7</TD>
                <TD width=3D"40%">UDP</TD></TR>
              <TR>
                <TD width=3D"40%">echo</TD>
                <TD width=3D"20%">7</TD>
                <TD width=3D"40%">TCP</TD></TR>