Re: [lwip-users] UDP bind error due to address and port reuse

[Noam Weissman]

Hi,

I do not understand the logic in your design. If you send data to one IP why 
use 5 different ports ?
Either send some header that differentiate the 5 messages and in one receive 
function filter them
to different recipient ?

As for your question:
First of all you listen on one single port, meaning you bind IP+port to one PCB.

Secondly when you send data you use udp_sendto (RAW API) or similar if you use 
Netconn or Socket API

The udp_sendto  function accepts IP and port:
      err_t udp_sendto(struct udp_pcb *pcb, struct pbuf *p,  ip_addr_t *dst_ip, 
u16_t dst_port)

As for reply UDP packets from remote you better add some data in the reply that 
will give you 
the correlation with the data sent.


Hope that helped.

BR,
Noam.


-----Original Message-----
From: Surya Chaitanya [mailto:address@hidden 
Sent: Wednesday, December 07, 2016 10:53 AM
To: Mailing list for lwIP users
Cc: Noam Weissman; address@hidden; address@hidden
Subject: Re: [lwip-users] UDP bind error due to address and port reuse

Hi Noam,

Our situation is something like this:

We have a Xilinx FPGA board. From one source port on the board, we would like 
to send 5 UDP request packets to 5 different destination port numbers on a PC. 
And, we would also like to receive 5 response packets, one from each of the 5 
ports on the PC to the single port on the FPGA board. Please let us know how to 
achieve this using the lwIP stack. Thank You.

Regards,
Surya




On Sat, 3 Dec 2016 12:56:52 +0000, Noam Weissman wrote
> Hi,
> 
> If I understand you correctly you are trying to bind IP:port several 
> times on the same machine
> 
> without closing the previous bind ?
> 
> This is not an option. You can bind UDP and TCP separately with two 
> different pcb's one for
> 
> TCP and one for UDP.
> 
> You cannot bind an IP:Port more then one time. This is the meaning of binding.
> 
> Its like a marriage between IP and a Port. Until you do not divorce 
> you cannot marry again [UTF-8?][😊]
> 
> BR,
> 
> Noam.
> 
> ________________________________
> From: lwip-users <address@hidden> on 
> behalf of Surya Chaitanya <address@hidden>
 Sent: Saturday, December 3, 2016 10:44 AM
 
> To: address@hidden
 Subject: [lwip-users] UDP bind error due to address 
> and port reuse
> 
> Hi,
> 
> I've been trying to use lwip to transfer UDP packets. In my situation, 
> in the client
 application, I would like to create 5 UDP PCBs having the same IP 
> address and port
 number. Inspite of setting the SO_REUSE flag to 1, and 
> setting the SOF_REUSEADDR flag
 to 1 for all the PCBs, the UDP bind error 
> still persists. Could somebody pls. help me
 out? Thank You.
> 
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