Re: [lwip-users] Socket recv of large message.

[Patrick Klos]

On 10/3/2017 4:47 AM, Flavio Gobber wrote:
> Hi lwip users,
>
> I have implemeted an application with lwip on a blackfin board.
> The stack is working with ping and TCP socket with short message, less 
> than 1400 bytes.
> I need to implement a server which need to receive message large more 
> than the length of 1400 bytes.
> What I see if the recv function return only a length of 1464 bytes, I 
> can repeat the the recv function before to parse the message, but how 
> can understand that the message is ended. This because the message 
> doesn't have the length information and the length could change 
> between a message and the Others.

TCP is a stream protocol, meaning that you can get any number of bytes 
at any time and there is no guarantee that they'll be received in the 
same sized chunks as they were sent.

You'll need to add length information to your protocol if the protocol 
has no other way to tell where "messages" start and stop.

Patrick Klos
Klos Technologies, Inc.