CODEWITHSUNDEEP
c++windowssockets
David Levy
David Levy

Reputation: 511

recvfrom in UDP not getting anything

i'm trying to receive data on a UDP socket, but I cant find a way to receive anything.

I can see with wireshark that the data is actually coming to the computer, but recvfrom always timeout.

The involved code is pretty simple :

mUDPSocket = socket( AF_INET, SOCK_DGRAM, IPPROTO_UDP );
if( mUDPSocket == INVALID_SOCKET )
    return 1;

uint32_t aTimeout = 5000;
const int lResult = setsockopt( mUDPSocket, SOL_SOCKET, SO_RCVTIMEO, ( char * )&aTimeout, sizeof( aTimeout ) );

if( SOCKET_ERROR == lResult )
    return 1;

struct sockaddr_in addr = {};
addr.sin_family = AF_INET;
addr.sin_addr.s_addr = htonl( INADDR_ANY ); //also tried with my local ip
addr.sin_port = htons( 48640 );

if( bind( mUDPSocket, ( const sockaddr * )&addr, sizeof( addr ) ) < 0 )
    return 1;

And later when trying to receive data 

if(recvfrom( mUDPSocket, ( char * )aData, aSize, 0, NULL, 0 )<0) //function return -1
    std::cout << WSAGetLastError() << std::endl; //10060

Im trying to do something basic, so I guess im missing something simple.

Edit : the packet is sent several time by second and the timeout is 5second, so I should receive it before the real timeout

I've attached a screen of the wireshark captureenter image description here

Upvotes: 2

Views: 4025

Answers (1)

Remy Lebeau
Remy Lebeau

Reputation: 597941

The only way I can see the code as shown timing out is if either:

  • the datagram is not arriving before aTimeout elapses (what is the actual value of aTimeout?)

  • the datagram is not using IPv4

  • the datagram is not being sent to an IP on the machine, or is not being sent to port 48640

  • the datagram is being blocked, such as by a firewall.

Upvotes: 4

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