4.4.6 接收数据

　　recvLine()函数实现接收一行数据的功能。在该函数中定义bLineEnd变量作为一行结束的标志。该变量和bConning变量一起作为While语句循环的条件。

将recv()函数的第3个参数设置为1，使得该函数每次仅接收一个字符。通过判断接收的字符是否为'/n'，来判断是否已经接收了一行数据。当接收字符为'/n'时，将bLineEnd设置为True。While语句循环结束，该函数返回True。

调用recv()函数失败时，调用break语句跳出while循环体，recvLine()函数返回值False。以该函数的返回值，判断是否成功地从客户端接收了一行数据。

当recv()函数返回值为0时，说明此时客户端的关闭了连接。

recvLine()函数程序清单如下。

/*

 *      读一行数据

 */

BOOL        RecvLine(SOCKET s, char* buf)

{

         BOOL        retVal = TRUE;                                                         //返回值

         BOOL        bLineEnd = FALSE;                                                 //行结束

         int              nReadLen = 0;                                                         //读入字节数

         int              nDataLen = 0;                                                          //数据长度

         while (!bLineEnd && bConning)                                                       //与客户端连接 没有换行

         {

                   nReadLen = recv(s, buf + nDataLen, 1, 0);//每次接收一个字节

                  

                   //错误处理

                   if (SOCKET_ERROR == nReadLen)

                   {

                            int nErrCode = WSAGetLastError();//错误代码

                            if (WSAENOTCONN == nErrCode)

                            {

                                     ShowSocketMsg("The socket is not connected!");

        

                            }else if(WSAESHUTDOWN == nErrCode)

                            {

                                     ShowSocketMsg("The socket has been shut down!");

        

                            }else if (WSAETIMEDOUT == nErrCode)

                            {

                                     ShowSocketMsg("The connection has been dropped!");

                            }else if (WSAECONNRESET == nErrCode)

                            {

                                     ShowSocketMsg("The virtual circuit was reset by the remote side!");

                            }else{}      

        

                            retVal = FALSE;                            //读数据失败

                            break;                                             //跳出循环

                   }

 

                   if (0 == nReadLen)                               //客户端关闭

                   {

                            retVal = FALSE;                            //读数据失败

                            break ;                                            //跳出循环

                   }

                  

                   //读入数据

                   if ('/n' == *(buf + nDataLen))                //换行符

                   {

                            bLineEnd = TRUE;                      //接收数据结束

                   }else{

                            nDataLen += nReadLen;           //增加数据长度

                   }

         }       

         return retVal;

}

注意：在调用Windows Sockets API时，如果调用函数失败，大多数函数返回SOCKET_ERROR。调用者可以使用WSAGetLastError()函数，获得错误代码。WSAGetLastError()函数得到最近一次操作失败时的错误代码。在下面的示例代码中，WSAGetLastError()函数使用是不正确的。

int retVal = listen(sServer, 2);

if(SOCKET_ERROR == retVal)

{

         closesocket(sServer);

         int nErrCode = WSAGetLastError();

         if (WSAENETDOWN == nErrCode)   //错误处理

         {

                   //处理

         }

}