recvfrom error

Re: UDP sendto/recvfrom error

Ben Bridgwater (bennyb@ntplx.net)
Tue, 13 Jul 1999 17:23:47 -0400

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• Maybe in reply to: Tracy Xiaodi Lu: "UDP sendto/recvfrom error"

---

Tracy Xiaodi Lu wrote:

> I hope someone can help to tell me why I met this error.
> ------------------OK---------------
> int client_len;
> int n=0;
> while(1)
> {
> if (n=recvfrom(sockfd,buffer,size,0,pclient_addr,&client_len))<=0)
> printf("error");
> sendto(.....)
> }
> ------------------ recvfrom error-----------
> int n=0;
> int client_len;
> while(1)
> {
> if (n=recvfrom(sockfd,buffer,size,0,pclient_addr,&client_len))<=0)
> printf("error");
> sendto(.....)
> }
> ------------------
>
> I found if I declare the int client_len right before the while loop, the
> recvfrom fucntion will return the "Invalid Argument" (22) error. But it
> works fine if I declare one of more variable after client_len.
>
>

client_len is used to pass in the size of the socket address buffer, as
well as return the actual length - you need to assign it before the
call.

Ben

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