Randomly get an available and free port

[lovelyelfpop]

If port is 0, can the server bind to a random free port?

Android

private static int findFreePort() {
        ServerSocket socket = null;
        try {
            socket = new ServerSocket(0);
            socket.setReuseAddress(true);
            int port = socket.getLocalPort();
            try {
                socket.close();
            } catch (IOException e) {
                // Ignore IOException on close()
            }
            return port;
        } catch (IOException e) {
        } finally {
            if (socket != null) {
                try {
                    socket.close();
                } catch (IOException e) {
                }
            }
        }
        throw new IllegalStateException("Could not find a free TCP/IP port to start embedded Jetty HTTP Server on");
    }

iOS

#import <netinet/in.h>


- (NSUInteger) _availablePort
{
    struct sockaddr_in addr4;
    bzero(&addr4, sizeof(addr4));
    addr4.sin_len = sizeof(addr4);
    addr4.sin_family = AF_INET;
    addr4.sin_port = 0; // set to 0 and bind to find available port
    addr4.sin_addr.s_addr = htonl(INADDR_ANY);

    int listeningSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
    if (bind(listeningSocket, (const void*)&addr4, sizeof(addr4)) == 0) {
        struct sockaddr addr;
        socklen_t addrlen = sizeof(addr);
        if (getsockname(listeningSocket, &addr, &addrlen) == 0) {
            struct sockaddr_in* sockaddr = (struct sockaddr_in*)&addr;
            close(listeningSocket);
            return ntohs(sockaddr->sin_port);
        }
    }

    return 0;
}