CODEWITHSUNDEEP
c++udp
fsxflyer789 Productions
fsxflyer789 Productions

Reputation: 125

Winsock always finding connection

I am trying to send a string over a udp socket in c++. Whenever i run this code, it always prints connection found infinitely. What am i doing wrong here? I'm not sure what it is seeing as a connection being made to it while listening or if something in my listening code is wrong? Any help would be appreciated :)

void main()

{
long sucessful;
WSAData WinSockData;
WORD DLLVERSION;

DLLVERSION = MAKEWORD(2, 1);

sucessful = WSAStartup(DLLVERSION, &WinSockData);

SOCKADDR_IN ADDRESS;
int cacheSize = sizeof(ADDRESS);

SOCKET sock_LISTEN;

SOCKET sock_CONNECTION;

sock_CONNECTION = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);

ADDRESS.sin_addr.s_addr = inet_addr("127.0.0.1");
ADDRESS.sin_family = AF_INET;
ADDRESS.sin_port = htons(444);

sock_LISTEN = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
bind(sock_LISTEN, (SOCKADDR*)&ADDRESS, sizeof(ADDRESS));
listen(sock_LISTEN, SOMAXCONN);

for (;;) {


    if (sock_CONNECTION = accept(sock_LISTEN,NULL, NULL)) {
        cout << "connection was found \n";
        sucessful = send(sock_CONNECTION, "I SEE YOU JAVA!", 100, NULL);
    }

    }



 }

Upvotes: 0

Views: 36

Answers (1)

Remy Lebeau
Remy Lebeau

Reputation: 596216

UDP is connection-less, you can't call listen() or accept() on a UDP socket. They will both fail and report WSAEOPNOTSUPP from WSAGetLastError().

You are ignoring errors from listen().

You are not testing the return value of accept() correctly. When accept() fails, it returns INVALID_SOCKET, which is defined as (SOCKET)(~0) (aka -1 casted to a SOCKET). Any non-zero value will evaluate as true in a boolean expression, such as an if statement.

There is no way to detect whether a UDP listener is running before you send packets to it. All you can do is unconditionally send packets and hope that responses are sent back.

Upvotes: 1

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