Question

I’ve searched all over google and can’t find a solution to this problem:

I’m trying to do some basic socket programming (client/server apps) on my Android device and I’m not having any luck starting the Server app. In my native code, I call bind(…) and I see from the log that it returns -1. When I check errno, the value is 97 (EAFNOSUPPORT), which indicates “Address family not supported by protocol.” When I checked the values for sin_family, it was AF_INET, which is IPv4. Is this not supported by the Android NDK? If not, what else could be the cause of this error?

Socket is initialized as:

sock = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP));

listenAddr is a sockaddr_in struct that’s initialized with:

sin_family = AF_INET;
sin_port = htons(9099);
sin_addr.s_addr = INADDR_NONE;

Call to bind:

bindResult = bind(sock, (sockaddr *)listenAddr, sizeof(listenAddr))

Bind result returns -1. Subsequent call to errno returns 97.

Answer 1

Use INADDR_ANY (or a specific interface’s address) rather than INADDR_NONE.

INADDR_NONE is an unsigned constant with the same bit pattern as the signed value -1, returned as an indication of error from certain calls.