网络传送bmp格式图片?

thegreatone 2012-01-05 02:52:57

各位大侠，我自己写的服务端和客户端，客户端请求服务端发送指定的文件，服务端接收请求将图片发送过去；现在问题出来了：
第一个问题，客户端接收的数据与服务端发送的数据有时会出现不一致，以至于图片显示错误；
第二个问题，如果我服务端设置套接字为非阻塞模式时，服务端有时会出现发送数据不完整的错误；
所以我想请教大侠，如何才能避免这些问题，谢谢！

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辰岡墨竹 2012-01-10

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你要自己定义个通信协议，发图片时指定尺寸、大小、色深什么的。然后发送完毕要有一个校验字（可以是CRC之类的）以及结束符。
如果错误就要求重发。
另外直接发BMP不太好，单线程又没有额外控制，这么大的失败率比较高。建议先压缩成png、jpg之类的再发送。
如果是连续的截图的话，可以考虑差分压缩，只传送图片改变的部分。

向立天 2012-01-10

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[Quote=引用 18 楼 thegreatone 的回复:]

目前，我的问题是不能完整接收数据包！
[/Quote]
你前面说了你的问题是粘包
所以需要定义包头包尾做区分
如果黏在一起了就按协议分开
如果没有接收完整就继续介绍
如果接收不到完整的包证明通信出错可以申请重发
以上都是通信协议应有的问题
你一味的强调“问题是不能完整接收数据包！”
用再多“！”号也只能说明你不是十分明白什么是通信协议

thegreatone 2012-01-10

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目前，我的问题是不能完整接收数据包！

向立天 2012-01-10

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这样的问题都是需要通过制定通信协议来解决的
每个数据包携带固定的数据
具有自己的意义
接收端按包解析出来即可
根据包头信息进行断包

King_hhuang 2012-01-10

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什么也不说了，直接上代码，自己研究一下吧



/*****************************************************************************\

 * hSocket:   套接字句柄

 * fName:    发送的本地文件路径

\*****************************************************************************/



BOOL SendFile(SOCKET hSocket, CString fName)

{

	BOOL bRet = TRUE;

 int fileLength, cbLeftToSend;



 // pointer to buffer for sending data (memory is allocated after sending file size)

 BYTE* sendData = NULL;

 CFile sourceFile;

 CFileException fe;

 BOOL bFileIsOpen = FALSE;



 if( !( bFileIsOpen = sourceFile.Open( fName, CFile::modeRead | CFile::typeBinary, &fe ) ) )

 {

  TCHAR strCause[256];

  fe.GetErrorMessage( strCause, 255 );

  TRACE( "SendFileToRemoteRecipient encountered an error while opening the local file\n"

   "\tFile name = %s\n\tCause = %s\n\tm_cause = %d\n\tm_IOsError = %d\n",

   fe.m_strFileName, strCause, fe.m_cause, fe.m_lOsError );

  

  /* you should handle the error here */

  

  bRet = FALSE;

  goto PreReturnCleanup;

 }

 

 // first send length of file

 fileLength = sourceFile.GetLength();

 fileLength = htonl( fileLength );

 cbLeftToSend = sizeof( fileLength );

 

 do

 {

  int cbBytesSent;

  const char* bp = (const char*)(&fileLength) + sizeof(fileLength) - cbLeftToSend;

  cbBytesSent = send(hSocket, bp, cbLeftToSend, 0);

  

  // test for errors and get out if they occurred

  if ( cbBytesSent == SOCKET_ERROR )

  {

   int iErr = ::GetLastError();

   TRACE( "SendFileToRemoteRecipient returned a socket error while sending file length\n"

    "\tNumber of Bytes sent = %d\n"

    "\tGetLastError = %d\n", cbBytesSent, iErr );

   

   /* you should handle the error here */



   bRet = FALSE;

   goto PreReturnCleanup;

  }

  

  // data was successfully sent, so account for it with already-sent data

  cbLeftToSend -= cbBytesSent;

 }

 while ( cbLeftToSend > 0 );

 

 // now send the file's data

 

 sendData = new BYTE[SEND_BUFFER_SIZE]; 

 

 cbLeftToSend = sourceFile.GetLength();

 

 do

 {

  // read next chunk of SEND_BUFFER_SIZE bytes from file

  

  int sendThisTime, doneSoFar, buffOffset;

  

  sendThisTime = sourceFile.Read( sendData, SEND_BUFFER_SIZE );

  buffOffset = 0;

  

  do

  {

   doneSoFar = send(hSocket, (const char*)(sendData + buffOffset), sendThisTime, 0); 

   

   // test for errors and get out if they occurred

   if ( doneSoFar == SOCKET_ERROR )

   {

    int iErr = ::GetLastError();

    TRACE( "SendFileToRemoteRecipient returned a socket error while sending chunked file data\n"

     "\tNumber of Bytes sent = %d\n"

     "\tGetLastError = %d\n", doneSoFar, iErr );

    

    /* you should handle the error here */

    

    bRet = FALSE;

    goto PreReturnCleanup;

   }

   

/***************************

  un-comment this code and put a breakpoint here to prove to yourself that sockets can send fewer bytes than requested

     

   if ( doneSoFar != sendThisTime )

   {

    int ii = 0;

   }

****************************/

   

   // data was successfully sent, so account for it with already-sent data

   

   buffOffset += doneSoFar;

   sendThisTime -= doneSoFar;

   cbLeftToSend -= doneSoFar;

  }

  while ( sendThisTime > 0 );

  

 }

 while ( cbLeftToSend > 0 );

 

 

PreReturnCleanup:  // labelled goto destination

 

 // free allocated memory

 // if we got here from a goto that skipped allocation, delete of NULL pointer

 // is permissible under C++ standard and is harmless

 delete[] sendData;

 

 if ( bFileIsOpen )

  sourceFile.Close();  // only close file if it's open (open might have failed above)

 

 return bRet;





}



/*****************************************************************************\

 * hSocket:   套接字句柄

 * fName:    要接收到本地的文件路径

\*****************************************************************************/



BOOL RecvFile(SOCKET hSocket, CString fName)

{

	BOOL bRet = TRUE;        // return value

 

 int dataLength, cbBytesRet, cbLeftToReceive; // used to monitor the progress of a receive operation

 

 BYTE* recdData = NULL; // pointer to buffer for receiving data (memory is allocated after obtaining file size)

 

 CFile destFile;

 CFileException fe;

 BOOL bFileIsOpen = FALSE;

 

 // open/create target file that receives the transferred data

 

 if( !( bFileIsOpen = destFile.Open( fName, CFile::modeCreate | CFile::modeWrite | CFile::typeBinary, &fe ) ) )

 {

  TCHAR strCause[256];

  fe.GetErrorMessage( strCause, 255 );

  

  AfxMessageBox(fName);



  CString strErrMsg;

  strErrMsg.Format("GetFileFromRemoteSender encountered an error while opening the local file\n"

   "\tFile name = %s\n\tCause = %s\n\tm_cause = %d\n\tm_IOsError = %d\n",

   fe.m_strFileName, strCause, fe.m_cause, fe.m_lOsError);



  AfxMessageBox( strErrMsg );

  

  /* you should handle the error here */

  

  bRet = FALSE;

  goto PreReturnCleanup;

 }

 

 

 // get the file's size first

 

 cbLeftToReceive = sizeof( dataLength );

 

 do

 {

  char* bp = (char*)(&dataLength) + sizeof(dataLength) - cbLeftToReceive;

  cbBytesRet = recv(hSocket, bp, cbLeftToReceive, 0);

  

  // test for errors and get out if they occurred

  if ( cbBytesRet == SOCKET_ERROR || cbBytesRet == 0 )

  {

   int iErr = ::GetLastError();

   CString strErr;

   strErr.Format("GetFileFromRemoteSite returned a socket error while getting file length\n"

    "\tNumber of Bytes received (zero means connection was closed) = %d\n"

    "\tGetLastError = %d\n", cbBytesRet, iErr );

  

   /* you should handle the error here */

   

   AfxMessageBox(strErr);



   bRet = FALSE;

   goto PreReturnCleanup;

  }

  

  // good data was retrieved, so accumulate it with already-received data

  cbLeftToReceive -= cbBytesRet;

  

 }

 while ( cbLeftToReceive > 0 );

 

 dataLength = ntohl( dataLength );

 

 

 // now get the file in RECV_BUFFER_SIZE chunks at a time

 

 recdData = new byte[RECV_BUFFER_SIZE];

 cbLeftToReceive = dataLength;

 

 do

 { 

  int iiGet, iiRecd;

  

  iiGet = (cbLeftToReceive<RECV_BUFFER_SIZE) ? cbLeftToReceive : RECV_BUFFER_SIZE ;

  iiRecd = recv(hSocket, (char *)recdData, iiGet, 0);

  

  // test for errors and get out if they occurred

  if ( iiRecd == SOCKET_ERROR || iiRecd == 0 )

  {

   int iErr = ::GetLastError();

   TRACE( "GetFileFromRemoteSite returned a socket error while getting chunked file data\n"

    "\tNumber of Bytes received (zero means connection was closed) = %d\n"

    "\tGetLastError = %d\n", iiRecd, iErr );

   

   /* you should handle the error here */

   

   bRet = FALSE;

   goto PreReturnCleanup;

  }



/************************* 

  un-comment this code and put a breakpoint here to prove to yourself that sockets can return fewer bytes than requested

    

   if ( iiGet != iiRecd )

   {

   int ii=0;

   }   

***************************/

  

  // good data was retrieved, so accumulate it with already-received data

  

  destFile.Write( recdData, iiRecd); // Write it

  cbLeftToReceive -= iiRecd;

  

 } 

 while ( cbLeftToReceive > 0 );

 

 

PreReturnCleanup:  // labelled "goto" destination

 

 // free allocated memory

 // if we got here from a goto that skipped allocation, delete of NULL pointer

 // is permissible under C++ standard and is harmless

 delete[] recdData;  



 if ( bFileIsOpen )

  destFile.Close(); // only close file if it's open (open might have failed above)



 return bRet;





}