CODEWITHSUNDEEP
linuxsockets
Christoph
Christoph

Reputation: 2004

Determine type of existing socket handle under Linux

Given only an existing/open socket handle, how can I determine whether the socket is a connection-oriented socket under Linux? I am searching for something like the WSAPROTOCOL_INFO under Windows, which I can retrieve using getsockopt.

Thanks in advance, Christoph

Upvotes: 1

Views: 602

Answers (2)

xaxxon
xaxxon

Reputation: 19761

int sock_type;
socklen_t sock_type_length = sizeof(sock_type);
getsockopt(socket, SOL_SOCKET, SO_TYPE, &sock_type, &sock_type_length);

if (sock_type == SOCK_STREAM) {
    // it's TCP or SCTP - both of which are connection oriented
} else if (sock_type == SOCK_DGRAM) {
    // it's UDP - not connection oriented
}

I suppose this is slightly simplistic, as there can be other protocols that can be stream or datagram, but this code is almost always what you want.

Upvotes: 3

Ottavio Campana
Ottavio Campana

Reputation: 4168

Taken from here:

Socket options

These socket options can be set by using setsockopt(2) and read with getsockopt(2) with the socket level set to SOL_SOCKET for all sockets:

...

SO_PROTOCOL (since Linux 2.6.32) Retrieves the socket protocol as an integer, returning a value such as IPPROTO_SCTP. See socket(2) for details. This socket option is read-only.

SO_TYPE Gets the socket type as an integer (e.g., SOCK_STREAM). This socket option is read-only.

To correct the solution provided by xaxxon, the code has to be:

int sock_type;
socklen_t sock_type_length = sizeof(sock_type);
getsockopt(socket, SOL_SOCKET, SO_TYPE, &sock_type, &sock_type_length);

if (sock_type == SOCK_STREAM) {
    getsockopt(socket, SOL_SOCKET, SO_PROTOCOL, &sock_type, &sock_type_length);
    if (sock_type == IPPROTO_TCP) {
        // it's TCP
    } else {
        // it's SCTP
    }
} else if (sock_type == SOCK_DGRAM) {
    // it's UDP
}

Upvotes: 1

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