TCP文件传输，源码，请帮忙找下错解决思路

TCP文件传输，源码，请帮忙找下错 - C++ Builder / Windows SDK/API
/****************文件数据接收线程******************/
void Thread5 ( PVOID pvoid )
{
int iiGet,iiRecd;
static char recvBuff[RECV_BUFFER_SIZE*4];


do
{
iiGet =( ToReceive<(RECV_BUFFER_SIZE*4) )? ToReceive : (RECV_BUFFER_SIZE*4) ; 
iiRecd=recv(tcp_client,recvBuff,iiGet,0); 
recvBuff[iiRecd]='\0';  
if (0!=iiRecd)
{
WriteFile(recvhFile,(LPVOID)recvBuff, iiGet,&dwBytesWrite,NULL);
if (0!=dwBytesWrite)
{
SendMessage(svProWnd1,PBM_STEPIT,(WPARAM)1,0);
}
iiRecd-=dwBytesWrite;
ToReceive -= dwBytesWrite;
}
else if (SOCKET_ERROR==iiRecd)
{
lstrcat (hisbuff,"\r\n");
lstrcat (hisbuff,"文件数据接收错误.....");
lstrcat (hisbuff,"\r\n");
SendMessage(showhwnd, EM_REPLACESEL, 0, (LPARAM) hisbuff) ;
SendMessage(hishwnd, EM_REPLACESEL, 0, (LPARAM) hisbuff) ;
iiRecd=0;
// setRecvZero();
SendMessage(recvDlg,WM_CLOSE,0,0);
}
}while(ToReceive>0);

if (ToReceive==0)
{
allFile--;
SendMessage(svProWnd2,PBM_STEPIT,(WPARAM)1,0);
CloseHandle(recvhFile);
}

if (allFile==0)
{
GetLocalTime(&sys);
sprintf_s(time,sizeof(time),"%2d:%2d:%2d",sys.wHour,sys.wMinute,sys.wSecond);

lstrcpy (hisbuff,time);
lstrcat (hisbuff,"\r\n");
lstrcat (hisbuff,"文件接收完毕......");
lstrcat (hisbuff,"\r\n");
SendMessage(showhwnd, EM_REPLACESEL, 0, (LPARAM) hisbuff) ;
SendMessage(hishwnd, EM_REPLACESEL, 0, (LPARAM) hisbuff) ;

process=TRUE;

SendMessage(recvDlg,WM_CLOSE,0,0);
}

closesocket(tcp_client);
_endthread () ;

}



/******************文件数据发送线程*****************/

void Thread6 ( PVOID pvoid )
{
int sendNum=0;
int k,l;
int sendthistime; 
HANDLE sendhFile; 
int buffOffset;
char errorCode[30];
static char lpBufPtr[SEND_BUFFER_SIZE*4]; //读入文件的缓冲区
toSendFileSize=0;

sendhFile=CreateFile(pathFile,GENERIC_READ,FILE_SHARE_READ,NULL,OPEN_EXISTING,FILE_ATTRIBUTE_READONLY,(HANDLE)NULL);  
k=GetLastError();
toSendFileSize=GetFileSize(sendhFile,NULL);


if(sendhFile!=INVALID_HANDLE_VALUE)  
{
do
{  
//把文件内容读入缓冲区  
memset(lpBufPtr,0,sizeof(lpBufPtr));
sendthistime=ReadFile(sendhFile,(LPVOID)lpBufPtr,SEND_BUFFER_SIZE*4,&dwBytesRead,NULL); 
lpBufPtr[dwBytesRead]='\0';
buffOffset=0;

//把内容装入多行编辑控件中  
if(dwBytesRead!=0)  
{  
do
{
sendda=send(tcp_client,(const char*)(lpBufPtr+buffOffset),dwBytesRead,0);  
l=GetLastError();
sendNum+=sendda;
if(sendda==SOCKET_ERROR)
{
lstrcat (hisbuff,"\r\n");
sprintf_s(errorCode,sizeof(errorCode),"文件数据发送错误，请重新发送.错误代码：%d",l);
lstrcat (hisbuff,errorCode);
lstrcat (hisbuff,"\r\n");
SendMessage(showhwnd, EM_REPLACESEL, 0, (LPARAM) hisbuff) ;
SendMessage(hishwnd, EM_REPLACESEL, 0, (LPARAM) hisbuff) ;
nextFile=TRUE;
//setZero();
sendda=0;
SendMessage(hDialog,WM_CLOSE,0,0);
}
buffOffset+=(sendda); //判断下次发送数据的指针
(int)dwBytesRead-=(sendda); //判断有无将所读取的内容发送完毕
toSendFileSize-=(sendda); //判断文件是否发送完毕
}while(dwBytesRead>0);
SendMessage(sendWnd,PBM_STEPIT,(WPARAM)1,0);
}  

else  
{
MessageBox(hWnd,TEXT("读入字节数为0 "),NULL,MB_OK|MB_ICONEXCLAMATION);  
}

}while(toSendFileSize>0);

if (toSendFileSize==0)
{
SendMessage(recvWnd,PBM_STEPIT,(WPARAM)1,0);
sendNumFile--;
nextFile=TRUE; //是否允许发送下一个文件 BOOL
}

if (sendNumFile==0)
{
GetLocalTime(&sys);
sprintf_s(time,sizeof(time),"%2d:%2d:%2d",sys.wHour,sys.wMinute,sys.wSecond);

lstrcpy (hisbuff,time);
lstrcat (hisbuff,"\r\n");
lstrcat (hisbuff,"文件发送完毕......");
lstrcat (hisbuff,"\r\n");

SendMessage(showhwnd, EM_REPLACESEL, 0, (LPARAM) hisbuff) ;
SendMessage(hishwnd, EM_REPLACESEL, 0, (LPARAM) hisbuff) ;

showDialog=TRUE;
sendcess=TRUE;
SendMessage(hDialog,WM_CLOSE,0,0);
}
}  
else  
{
MessageBox(hWnd,TEXT("发送文件：打开文件失败！ "),NULL,MB_OK|MB_ICONEXCLAMATION);
SendMessage(hDialog,WM_CLOSE,0,0);
}

CloseHandle(sendhFile);
closesocket(tcp_client);
_endthread () ;

}

文件发送，接收各有一线程负责；
为什么在发送，接收时，有时能成功，有时失败；
文件大小都能保证，但是，有时文件却打不开，如一rar文件，不能解压；
或一rmvb不能正常播放

[解决办法]
//这里实际接收到的字节数为iiRecd
iiRecd=recv(tcp_client,recvBuff,iiGet,0); 
recvBuff[iiRecd]='\0';
if (0!=iiRecd) 
{ 
//写入文件时就应该也是iiRecd
WriteFile(recvhFile,(LPVOID)recvBuff, iiGet,&dwBytesWrite,NULL);