SOCKET 的封裝

C++ 通用框架的設計 作者： naven

1?????????? SOCKET 封裝介紹

Socket 通訊程序估計現在大多數應用系統都會涉及到，因為現在的世界是一個由 Internet 網絡連接的世界，任何個人電腦或服務都可能會有數據交換，通過 TCP/UDP 這樣的 Socket 通訊協議進行聯系。開發這樣的通訊程序會是很普遍也很類似，每種操作系統都實現了 Socket 通訊庫并提供很相似的 API ，通訊步驟都遵循 RFC 規范。但是有些 API 的具體接口卻稍有不同，比如 Socket IO API 在 win32 系統和 Unix 系統就不一樣， Win32 用 recv/send 而 Unix 使用標準統一的 read/write ，而且 socket 句柄在不同操作系統處理也不一樣，等等這些都造成編寫跨平臺的 Socket 應用不太容易。另外編寫服務器和客戶端的處理步驟也很繁瑣， IP 地址和域名的轉換也很麻煩，所以實現一個標準統一使用更簡潔的 API 非常有用。本 C++ 框架基本參考 Java 的 Socket 相關類實現了類似封裝，除了 ServerSocket 實現稍有不同，其他原理和方法基本類似。用它編寫網絡應用基本不用考慮底層的協議處理，使用非常容易，代碼也更簡潔易讀。

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主要有如下一些類

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class Socket ?????????????????????? ??????????????????????????? 代表一個 TCP 連接的 Socket 對象

???????? class DatagramSocket??????????????????????????????????? 代表一個 UDP 連接的 Socket 對象（暫未實現）

???????? class MulticastSocket??????????????????????????????????? 一個 DatagramSocket 的子類用于多播（暫未實現）

class SocketAcceptor??????????????????????????????????? 一個 TCP 服務端的接收器

class SocketConnector????????????????????????????????? 一個 TCP 客戶端的連接器

???????? class SocketInputStream?????????????????????????????? 一個 Socket 連接的輸入流

???????? class SocketOutputStream??????????????????????????? 一個 Socket 連接的輸出流

???????? class SocketReader??????????????????????????????????????? 一個 Socket 連接的讀操作器

???????? class SocketWriter????????????????????????????????????????? 一個 Socket 連接的寫操作器

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Socket 的意思是在網絡的機器之間建立一個通信線路。通過 TCP Sockets 發送或接收的操作時通過 InputStream 和 OutputStream 流處理的， Socket 類的 getInputStream 和 getOutputStream 可以取得該 Socket 連接的輸入 / 輸出流對象。 SocketAcceptor 是用于服務器端的接收器，它處于接收的狀態時會阻塞，直到接收到客戶端的連接請求，這時就會創建一個 Socket 對象代表該服務器到此客戶端的連接。而對應的 SocketConnector 是用于客戶端的連接器，它向服務端發出連接請求，如果服務器允許連接，則也同時建立一個 Socket 對象表示它到服務器端的連接，這時就可以獲取輸入 / 輸出流對象進行 Socket 通訊了。

2?????????? Hello World!

下面的程序示例如何用上面的類進行 Scoket 通訊：

這是服務端的實現

void ?servertest()?
{
???? // ?定義一個接收器綁定?8000?端口
????SocketAcceptor?sa( 8000 );?
???? while ( 1 )?
{
??????? // ?阻塞等待連接請求
????????Socket?sk? = ?sa.accept();?
???????? // ?獲取此連接的讀操作器和寫操作器
????????Reader? & rd? = ?sk.getReader();?
????????Writer? & wr? = ?sk.getWriter();?
????????String?s;?
???????? // ?從客戶端讀取?10?個字節
????????rd.read(s,? 10 );?
???????? // ?向客戶端寫信息
????????wr.write(“read?ok”);?
???????? // ?關閉連接
????????sk.close();?
}
}

這是客戶端的實現

void ?clienttest()
{
???? // ?定義一個連接器
SocketConnector?sc;?
// ?連接指定的服務器地址及端口,?返回一個Socket對象
Socket?sk? = ?sc.connect(“localhost”,? 8000 );?
// ?如果已成功連上
???? if (?sk.isConnected()?)?
{
???? // ?獲取此連接的讀操作器和寫操作器
????????Reader & ?reader? = ?sk.getReader();?
????????Writer & ?writer? = ?sk.getWriter();?
???????? // ?可以在讀操作器上建立一個帶緩沖的讀操作器
????????BufferedReader?rd(reader);
???????? // ?向服務器發送信息
????????writer.write(“hello?server”);
???????? // ?接收信息,?帶緩沖的讀操作器可以讀取一行
????????rd.readLine(s);
???????? // ?關閉連接
????????sk.close();
????}
}

1?????????? Socket 類

此類定義一個表示 Socket 連接的類，一個 Socket 是一個為在兩臺機器間通信的端點。一個 Socket 類的真實行為是通過一個 SocketImpl 類的詩體執行的。一個應用程序可以通過改變 Socket Factory 來創建 Socket 的具體實現，以適應本地的局域網防火墻。

Socket 類成員和主要接口定義如下：

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class ?Socket?:? public ?AbstractFile?
{
protected :?
???? /**/ /* *
?????*?The?implementation?of?this?Socket.
????? */
????SocketImplAutoPtr?_impl;?

???? /**/ /* *
?????*?Various?states?of?this?socket.
????? */
????BOOL?_connected;?
????BOOL?_closed;?
????BOOL?_shutIn;?
BOOL?_shutOut;

public :?
???? /**/ /* *
?????*?Creates?an?unconnected?socket,?with?the
?????*?system-default?type?of?SocketImpl.
????? */
Socket();

???? /**/ /* *
?????*?Returns?an?input?stream?for?this?socket.
?????*
?????*?@return?????an?input?stream?for?reading?bytes?from?this?socket.
????? */
????InputStream & ?getInputStream();

???? /**/ /* *
?????*?Gets?an?Reader?for?this?socket.
????? */
????Reader & ?getReader();

???? /**/ /* *
?????*?Returns?an?output?stream?for?this?socket.
?????*
?????*?@return?????an?output?stream?for?writing?bytes?to?this?socket.
????? */
????OutputStream & ?getOutputStream();

???? /**/ /* *
?????*?Gets?an?Writer?for?this?socket.
????? */
????Writer & ?getWriter();?

???? /**/ /* *
?????*?Enable/disable?the?option?specified?by?<I>optID</I>.??If?the?option
?????*?is?to?be?enabled,?and?it?takes?an?option-specific?"optval",??this?is
?????*?passed?in?<I>value</I>.??The?actual?type?of?value?is?option-specific,
?????*?and?it?is?an?error?to?pass?something?that?isn't?of?the?expected?type:
?????*?<BR>
?????*
?????*?@param?optID?identifies?the?option
?????*?@param?level?[in]?Level?at?which?the?option?is?defined;?the?supported?levels?
?????*??????????????include?SOL_SOCKET?and?IPPROTO_TCP.?
?????*?@param?optval?[in]?Pointer?to?the?buffer?in?which?the?value?for?the?requested?
?????*??????????????option?is?to?be?returned.
?????*?@param?optlen?[in]?Pointer?to?the?size?of?the?optval?buffer,?in?bytes.?
?????*?@return?0?If?no?error?occurs,?Otherwise,?a?value?of?SOCKET_ERROR(-1)?is?returned,?
?????*??????????and?a?specific?error?code?can?be?retrieved?by?socketerrno.
?????*?@see?#getOption(int)
????? */
???? int ?setOption( int ?optID,? int ?level,? const ? void ? * optval,? int ?optlen);

???? /**/ /* *
?????*?Fetch?the?value?of?an?option.
?????*?Binary?options?will?return?java.lang.Boolean(true)
?????*?if?enabled,?java.lang.Boolean(false)?if?disabled,?e.g.:
?????*?<BR>
?????*
?????*?@param?optID?an?<code>int</code>?identifying?the?option?to?fetch
?????*?@param?level?[in]?Level?at?which?the?option?is?defined;?the?supported?levels?
?????*??????????????include?SOL_SOCKET?and?IPPROTO_TCP.?
?????*?@param?optval?[out]?Pointer?to?the?buffer?in?which?the?value?for?the?requested?
?????*??????????????option?is?to?be?returned.
?????*?@param?optlen?[in,?out]?Pointer?to?the?size?of?the?optval?buffer,?in?bytes.?
?????*?@return?0?If?no?error?occurs,?Otherwise,?a?value?of?SOCKET_ERROR(-1)?is?returned,?
?????*??????????and?a?specific?error?code?can?be?retrieved?by?socketerrno.
?????*?@see?#setOption(int,?java.lang.Object)
????? */
???? int ?getOption( int ?optID,? int ?level,? void ? * optval,? int ? * optlen);

???? /**/ /* *
?????*?Closes?this?socket.
?????*?<p>
?????*?Any?thread?currently?blocked?in?an?I/O?operation?upon?this?socket
?????*?will?throw?a?{@link?SocketException}.
?????*?<p>
?????*?Once?a?socket?has?been?closed,?it?is?not?available?for?further?networking
?????*?use?(i.e.?can't?be?reconnected?or?rebound).?A?new?socket?needs?to?be
?????*?created.
?????*
?????*?<p>?If?this?socket?has?an?associated?channel?then?the?channel?is?closed
?????*?as?well.
?????*
????? */
???? void ?close();

} ;

1?????????? SocketAcceptor類

此類實現一個用于服務器端接收連接的類。一個SocketAcceptor對象等待來自網絡的連接請求，它執行一些基于請求的操作，并且可能返回一些信息給請求者。連接成功后SocketAcceptor會生成一個Socket對象用于網絡通訊。

SocketAcceptor類成員和主要接口定義如下：

?

class?SocketAcceptor
{
protected:?
????/**//**
?????*?The?factory?for?all?server?sockets.
?????*/
????static?SocketImplFactoryAutoPtr?_factory;?

????/**//**
?????*?The?implementation?of?this?Socket.
?????*/
????SocketImplAutoPtr?_impl;?

????/**//**
?????*?Various?states?of?this?socket.
?????*/
????BOOL?_bound;?
????BOOL?_created;?
????BOOL?_closed;?
????BOOL?_stream;?

public:?
????/**//**
?????*?Creates?a?socket?acceptor?with?default?stream?type.
?????*?<p>
?????*/
????SocketAcceptor();?

????/**//**
?????*?Creates?a?socket?acceptor?with?specified?stream?type,?
?????*?bound?to?the?specified?port?and?host.?A?port?of?
?????*?<code>0</code>?creates?a?socket?on?any?free?port.?
?????*?<p>
?????*?The?maximum?queue?length?for?incoming?connection?indications?(a?
?????*?request?to?connect)?is?set?to?<code>50</code>.?If?a?connection?
?????*?indication?arrives?when?the?queue?is?full,?the?connection?is?refused.
?????*?<p>
?????*?If?the?application?has?specified?a?server?socket?factory,?that?
?????*?factory's?<code>createSocketImpl</code>?method?is?called?to?create?
?????*?the?actual?socket?implementation.?Otherwise?a?"plain"?socket?is?created.
?????*?<p>
?????*
?????*?@param??????host?the?host?address?the?server?will?bind?to
?????*?@param??????port??the?port?number,?or?<code>0</code>?to?use?any
?????*???????????????????free?port.
?????*?@param??????stream????if?<code>true</code>,?create?a?stream?socket;
?????*???????????????????????otherwise,?create?a?datagram?socket.
?????*?@param??????backlog?the?listen?backlog
?????*/
SocketAcceptor(const?String?&host,?int?port,?BOOL?stream?=?TRUE);

????/**//**
?????*?Binds?the?<code>ServerSocket</code>?to?a?local?address
?????*?(IP?address?and?port?number).
?????*?<P>
?????*?The?<code>backlog</code>?argument?must?be?a?positive
?????*?value?greater?than?0.?If?the?value?passed?if?equal?or?less
?????*?than?0,?then?the?default?value?will?be?assumed.
?????*?@param?port?the?local?TCP?port
?????*?@param?backlog?the?listen?backlog
?????*?@return?0?If?no?error?occurs,?Otherwise,?a?value?of?
?????*??????????SOCKET_ERROR(-1)?is?returned
?????*/
????int?bind(int?port,?int?backlog?=?LISTENQ);

????/**//**
?????*?Listens?for?a?connection?to?be?made?to?this?socket?and?accepts?
?????*?it.?The?method?blocks?until?a?connection?is?made.?
?????*
?????*?<p>A?new?Socket?<code>s</code>?is?created?and,?if?there?
?????*?is?a?security?manager,?
?????*?the?security?manager's?<code>checkAccept</code>?method?is?called
?????*?with?<code>s.getInetAddress().getHostAddress()</code>?and
?????*?<code>s.getPort()</code>
?????*
?????*?@param?timeout??timeout?to?accept?in?ms.?
?????*?@return?the?new?Socket
?????*/
????Socket?accept(int?timeout);?

????/**//**
?????*?Closes?this?socket?acceptor.
?????*?<p>
?????*?Any?thread?currently?blocked?in?an?I/O?operation?upon?this?socket
?????*?will?throw?a?{@link?SocketException}.
?????*?<p>
?????*?Once?a?socket?has?been?closed,?it?is?not?available?for?further?networking
?????*?use?(i.e.?can't?be?reconnected?or?rebound).?A?new?socket?needs?to?be
?????*?created.
?????*
?????*?<p>?If?this?socket?has?an?associated?channel?then?the?channel?is?closed
?????*?as?well.
?????*
?????*/
????void?close();

};

1?????????? SocketConnector類

此類實現一個用于客戶器端連接服務的類。一個SocketConnector對象可以向指定的服務地址和端口發出的連接請求，它執行一些基于請求的操作，并且可能返回一些信息。連接成功后SocketConnector會生成一個Socket對象用于網絡通訊。

SocketConnector類成員和主要接口定義如下：

class?SocketConnector
{
protected:?
????/**//**
?????*?The?factory?for?all?server?sockets.
?????*/
????static?SocketImplFactoryAutoPtr?_factory;?

????/**//**
?????*?The?implementation?of?this?Socket.
?????*/
????SocketImplAutoPtr?_impl;?

????/**//**
?????*?Various?states?of?this?socket.
?????*/
????BOOL?_bound;?
????BOOL?_created;?
????BOOL?_closed;?
????BOOL?_stream;;?

public:?
????/**//**
?????*?Creates?a?socket?connector?with?specified?stream?type.
?????*?default?is?Creates?a?stream?socket?connector.?
?????*?<p>
?????*
?????*?@param??????stream????if?<code>true</code>,?create?a?stream?socket;
?????*???????????????????????otherwise,?create?a?datagram?socket.
?????*/
????SocketConnector(BOOL?stream?=?TRUE);

????/**//**
?????*?Creates?a?socket?and?connects?it?to?the?specified?port?on
?????*?the?specified?host.
?????*?@param?host?the?specified?host
?????*?@param?port?the?specified?port
?????*?@param?timeout?the?timeout?value?in?milliseconds,?or?zero?for?no?timeout.
?????*??????????-1?will?use?default?timeout.
?????*?@return?the?new?Socket
?????*/
Socket?connect(const?String?&host,?int?port,?int?timeout?=?-1);

????/**//**
?????*?Closes?this?socket?connector.
?????*?<p>
?????*?Any?thread?currently?blocked?in?an?I/O?operation?upon?this?socket
?????*?will?throw?a?{@link?SocketException}.
?????*?<p>
?????*?Once?a?socket?has?been?closed,?it?is?not?available?for?further?networking
?????*?use?(i.e.?can't?be?reconnected?or?rebound).?A?new?socket?needs?to?be
?????*?created.
?????*
?????*?<p>?If?this?socket?has?an?associated?channel?then?the?channel?is?closed
?????*?as?well.
?????*
?????*/
????void?close();

};

1?????????? SocketInputStream類

這個類類似與其他InputStream如FileInputStream類，是InputStream接口類的一個實現，執行Socket流的讀取操作，實現的接口均是最基礎的操作，如讀取一個byte字節的數據，或者讀取指定長度的數據。

SocketInputStream類成員和主要接口定義如下：

class?SocketInputStream?:?public?InputStream
{
protected:?
????/**//**
?????*?Pointer?to?the?implementation?of?this?SocketImpl.
?????*/
????PlainSocketImpl?*_impl;?

????/**//**
?????*?Pointer?to?the?implementation?of?this?Socket.
?????*/
????Socket?*_socket;?

????BOOL?_eof;?
BOOL?_closing;

????/**//**
?????*?Creates?a?new?SocketInputStream.?Can?only?be?called
?????*?by?a?Socket.?This?method?needs?to?hang?on?to?the?owner?Socket?so
?????*?that?the?fd?will?not?be?closed.
?????*?@param?impl?the?implemented?socket?input?stream
?????*/
????SocketInputStream(PlainSocketImpl?&impl);

public:?
????/**//**
?????*?Check?current?SocketInputStream?object?if?is?opened.?
?????*
?????*?@return??TRUE?if?opened?else?return?FALSE
?????*/
????BOOL?isOpened();

????/**//**
?????*?Reads?a?byte?of?data?from?this?input?stream.?This?method?blocks
?????*?if?no?input?is?yet?available.
?????*
?????*?@return?????the?next?byte?of?data,?or?<code>-1</code>?if?the?end?of?the
?????*?????????????file?is?reached.
?????*/
????int?read();?

????/**//**
?????*?Reads?up?to?<code>len</code>?bytes?of?data?from?this?input?stream
?????*?into?an?array?of?bytes.?This?method?blocks?until?some?input?is
?????*?available.
?????*
?????*?@param??????b?????the?buffer?into?which?the?data?is?read.
?????*?@param??????off???the?start?offset?of?the?data.
?????*?@param??????len???the?maximum?number?of?bytes?read.
?????*?@return?????the?total?number?of?bytes?read?into?the?buffer,?or
?????*?????????????<code>0</code>?if?there?is?no?more?data?because?the?end?of
?????*?????????????the?file?has?been?reached,?or?-1?if?read?error.
?????*/
????int?read(void?*b,?int?off,?int?len);

????/**//**
?????*?Reads?up?to?<code>len</code>?bytes?of?data?from?this?input?stream
?????*?into?an?array?of?bytes.?This?method?blocks?until?some?input?is
?????*?available.
?????*
?????*?@param??????b?????the?buffer?into?which?the?data?is?read.
?????*?@param??????len???the?maximum?number?of?bytes?read.
?????*?@return?????the?total?number?of?bytes?read?into?the?buffer,?or
?????*?????????????<code>0</code>?if?there?is?no?more?data?because?the?end?of
?????*?????????????the?file?has?been?reached,?or?-1?if?read?error.
?????*/
????int?read(void?*b,?int?len);

????/**//**
?????*?Skips?over?and?discards?<code>n</code>?bytes?of?data?from?the
?????*?input?stream.?The?<code>skip</code>?method?may,?for?a?variety?of
?????*?reasons,?end?up?skipping?over?some?smaller?number?of?bytes,
?????*?possibly?<code>0</code>.?The?actual?number?of?bytes?skipped?is?returned.
?????*
?????*?@param??????n???the?number?of?bytes?to?be?skipped.
?????*?@return?????the?actual?number?of?bytes?skipped.
?????*/
????long?skip(long?n);?

????/**//**
?????*?Returns?the?number?of?bytes?that?can?be?read?from?this?file?input
?????*?stream?without?blocking.
?????*
?????*?@return?????the?number?of?bytes?that?can?be?read?from?this?file?input
?????*?????????????stream?without?blocking.
?????*/
????int?available();?

????/**//**
?????*?Closes?this?file?input?stream?and?releases?any?system?resources
?????*?associated?with?the?stream.
?????*
?????*?<p>?If?this?stream?has?an?associated?channel?then?the?channel?is?closed
?????*?as?well.
?????*/
????void?close();

};

?

1?????????? SocketOutputStream類

這個類類似與其他OutputStream如FileOutputStream類，是OutputStream接口類的一個實現，執行Socket流的寫操作，實現的接口均是最基礎的操作，如寫一個byte字節的數據，或者寫指定長度的數據。

SocketOutputStream類成員和主要接口定義如下：

?

class?SocketOutputStream?:?public?OutputStream
{
protected:?
????/**//**
?????*?Pointer?to?the?implementation?of?this?SocketImpl.
?????*/
????PlainSocketImpl?*_impl;?

????/**//**
?????*?Pointer?to?the?implementation?of?this?Socket.
?????*/
Socket?*_socket;

????/**//**
?????*?Creates?a?new?SocketOutputStream.?Can?only?be?called
?????*?by?a?Socket.?This?method?needs?to?hang?on?to?the?owner?Socket?so
?????*?that?the?fd?will?not?be?closed.
?????*?@param?impl?the?implemented?socket?input?stream
?????*/
????SocketOutputStream(PlainSocketImpl?&impl);

public:?
????/**//**
?????*?Check?current?SocketInputStream?object?if?is?opened.?
?????*
?????*?@return??TRUE?if?opened?else?return?FALSE
?????*/
????BOOL?isOpened();?

????/**//**
?????*?Report?position?in?output?stream.
?????*/?
long?tellp();

????/**//**
?????*?Writes?the?specified?byte?to?this?file?output?stream.?Implements?
?????*?the?<code>write</code>?method?of?<code>OutputStream</code>.
?????*
?????*?@param?b???the?byte?to?be?written.
?????*/
????SocketOutputStream&?write(int?b);?

????/**//**
?????*?Writes?<code>len</code>?bytes?from?the?specified?byte?array?
?????*?starting?at?offset?<code>off</code>?to?this?file?output?stream.?
?????*
?????*?@param??????b?????the?data.
?????*?@param??????len???the?number?of?bytes?to?write.
?????*/
????SocketOutputStream&?write(const?void?*b,?int?len);?

????/**//**
?????*?Writes?<code>len</code>?bytes?from?the?specified?byte?array?
?????*?starting?at?offset?<code>off</code>?to?this?file?output?stream.?
?????*
?????*?@param??????b?????the?data.
?????*?@param??????off???the?start?offset?in?the?data.
?????*?@param??????len???the?number?of?bytes?to?write.
?????*/
????SocketOutputStream&?write(const?void?*b,?int?off,?int?len);?

????/**//**
?????*?Flushes?this?output?stream?and?forces?any?buffered?
?????*?output?bytes?to?be?written?out.
?????*/
????void?flush();?

????/**//**
?????*?Closes?this?file?out?stream?and?releases?any?system?resources
?????*?associated?with?the?stream.
?????*
?????*?<p>?If?this?stream?has?an?associated?channel?then?the?channel?is?closed
?????*?as?well.
?????*/
????void?close();

};

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1?????????? SocketReader類和SocketWriter類

SocketReader類實現了一個對Socket流讀設備即SocketInputStream的讀取器，它實現了Reader接口類的方法，所以具有與其它Reader相同的功能，也可以與其它一些讀操作器如BufferedReader配合使用以達到一些更高級的功能。

SocketWriter 類則實現了一個對Socket流寫設備即SocketOutputStream的寫操作器，它實現了Writer接口類的方法，所以具有與其它Writer相同的功能，如進行一些operator <<運算符的操作等。

詳細例子請參考 httptest.cpp 范例程序。

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C++通用框架的設計作者：naven 日期：2006-8-10

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