RE: My client can not receive data in blocking mode

[Michael Wojcik]

From: openssl-users [mailto:openssl-users-boun...@openssl.org] On Behalf Of 
l...@e-code.net
Sent: Friday, September 27, 2019 11:42

> The data seems be cached on the server and not be sent out.

Is it? Have you run a network trace? Have you tried waiting longer than 100ms?

If your server is sending a segment shorter than the MSS, you may be seeing 
Nagle / Delayed ACK interaction. If that's holding up the end of a TLS record, 
then select will indicate the socket is readable but a subsequent SSL_read will 
block until the remainder of the record has been received.

A network trace, even without decryption, will give you some idea of when data 
is being sent, and how much.

--
Michael Wojcik
Distinguished Engineer, Micro Focus

Re: My client can not receive data in blocking mode

[John Unsworth]

You do not say what OS you are running on. Solaris 11 has a known problem with 
not reporting queued data. This was fixed by SRU-28.

Regards,
John Unsworth

From: openssl-users  on behalf of 路连峰 

Sent: Monday, September 23, 2019 4:55 am
To: openssl-users
Subject: My client can not receive data in blocking mode

Hello

I'm using openssl as client in blocking mode , i have a problem .
Sometimes my program can't  receive data , and acctually server has been sent 
the data to me.
I can only  receive the data by sending another request . Then the data i 
expected arrived with a new data sent by server .

--
bool can_read()
{
  if(SSL_pending(m_ssl))
return true;
struct timeval tv = {0 , 100};
   FD_ZERO(&m_rfds);
   FD_SET(m_socket.fd(), &m_rfds);
int ret = select( m_socket.fd()+1, &m_rfds , NULL, NULL, &tv);
return ret > 0 ;
}

//this is the main process
int try_receive(char * buf , int len )
{
if( !can_read())
return -1;

return SSL_read(m_ssl, buf, len);
}
---
 Above is my code ,  my program get `false` from `can_read` although the server 
has sent response data
 I really appreciate your help.