CCS/TI-RTOS-MCU: Web Server receive post data for file fail

Part Number:TI-RTOS-MCU

Tool/software: Code Composer Studio

Web socket can't receive vast data,it is  more than its receiveBufSize.  A  file is 16KB. I pass it by Web . Web pass it by post .  I reveice the post data . now I can't reveice it . if a file is 1KB. I revece it OK.

my receiveBufSize = 2920;

my code :

while(iNumParams)
{
     data_legnth = recv(htmlSock, pcParam, 1460, 0);
     iNumParams=iNumParams-data_legnth;

    ......//do some  thing
}

Web code:

<form action="cacer1.cgi" method="post" name="cacer" enctype="multipart/form-data"> 
<div class="top_content" style="height:auto">
<div class="top">
<p>Firmware Upgrading</p>
</div>
<table width="100%" height="auto" border="0" bordercolor="#CCCCCC">
<tr>
<td width="30%" class="gr"><div align="right">
<div> Firmware Upgrading:</div>
</div></td>
<td width="70%"><div align="left">
<input type="file" name="sca" id="sercer" > 
<button class="button" type="submit">Upgrade</button>
</div></td>

</tr> 
</table>
</div>
</form>

Wireshark    192.168.2.242 is my mcu        192.168.2.204 is my pc