iPhone在个人热点模式下未发送网络广播/多播

我在iOS 10上广播正常工作

我要发布第二个答案，因为我找到了一种在个人热点模式下在iOS 10上进行广播的方法.解决方案有点复杂，但是这就是我的工作方式:

I'm posting a second answer, because I found a way to get broadcast working on iOS 10 in personal hotspot mode. the solution is a bit complex, but here is how I got it to work:

1. 使用 getifaddrs(if)遍历所有接口( do {} while(if = if-> ifa_next))
2. 拒绝回送接口( if-> ifa_flags和IFF_LOOPBACK )
3. 仅过滤支持广播的接口( if-> ifa_flags和IFF_BROADCAST )
4. 使用 int sock = socket()
创建一个套接字
5. 启用广播: int yes = 1;setsockopt(袜子，SOL_SOCKET，SO_BROADCAST，&是，sizeof是)
6. 连接到广播地址: connect(sock，if-> ifa_dstaddr，if-> ifa_dstaddr-> sa_len)
7. 现在使用 send()发送您的消息！

1. use getifaddrs(if) to loop through all interfaces (do {} while (if = if->ifa_next))
2. reject loopback interfaces (if->ifa_flags & IFF_LOOPBACK)
3. filter only interfaces that support broadcast (if->ifa_flags & IFF_BROADCAST)
4. create a socket with int sock = socket()
5. enable broadcast: int yes = 1; setsockopt(sock, SOL_SOCKET, SO_BROADCAST, &yes, sizeof yes)
6. connect to the broadcast address: connect(sock, if->ifa_dstaddr, if->ifa_dstaddr->sa_len)
7. now use send() to send your message!

我已经确认这既可以在iPhone连接到WiFi网络时使用，也可以在个人热点模式下使用.

I've confirmed that this works both when the iPhone is connected to a WiFi network, and also when it's in personal hotspot mode.

完整示例代码

#include <ifaddrs.h>
#include <arpa/inet.h>
#include <net/if.h>

-(IBAction)sayHello:(id)sender {

    // fetch a linked list of all network interfaces
    struct ifaddrs *interfaces;
    if (getifaddrs(&interfaces) == -1) {
        NSLog(@"getifaddrs() failed: %s", strerror(errno));
        return;
    }

    // loop through the linked list
    for(struct ifaddrs *interface=interfaces; interface; interface=interface->ifa_next) {

        // ignore loopback interfaces
        if (interface->ifa_flags & IFF_LOOPBACK) continue;

        // ignore interfaces that don't have a broadcast address
        if (!(interface->ifa_flags & IFF_BROADCAST) || interface->ifa_dstaddr == NULL) continue;

        // check the type of the address (IPv4, IPv6)
        int protocol_family;
        struct sockaddr_in ipv4_addr = {0};
        struct sockaddr_in6 ipv6_addr = {0};
        struct sockaddr *addr;
        if (interface->ifa_dstaddr->sa_family == AF_INET) {
            if (interface->ifa_dstaddr->sa_len > sizeof ipv4_addr) {
                NSLog(@"Address too big");
                continue;
            }
            protocol_family = PF_INET;
            memcpy(&ipv4_addr, interface->ifa_dstaddr, interface->ifa_dstaddr->sa_len);
            ipv4_addr.sin_port = htons(16000);
            addr = (struct sockaddr *)&ipv4_addr;

            char text_addr[255] = {0};
            inet_ntop(AF_INET, &ipv4_addr.sin_addr, text_addr, sizeof text_addr);
            NSLog(@"Sending message to %s:%d", text_addr, ntohs(ipv4_addr.sin_port));
        }
        else if (interface->ifa_dstaddr->sa_family == AF_INET6) {
            if (interface->ifa_dstaddr->sa_len > sizeof ipv6_addr) {
                NSLog(@"Address too big");
                continue;
            }
            protocol_family = PF_INET6;
            memcpy(&ipv6_addr, interface->ifa_dstaddr, interface->ifa_dstaddr->sa_len);
            ipv6_addr.sin6_port = htons(16000);
            addr = (struct sockaddr *)&ipv6_addr;

            char text_addr[255] = {0};
            inet_ntop(AF_INET6, &ipv6_addr.sin6_addr, text_addr, sizeof text_addr);
            NSLog(@"Sending message to %s:%d", text_addr, ntohs(ipv6_addr.sin6_port));
        }
        else {
            NSLog(@"Unsupported protocol: %d", interface->ifa_dstaddr->sa_family);
            continue;
        }

        // create a socket
        int sock = socket(protocol_family, SOCK_DGRAM, IPPROTO_UDP);
        if (sock == -1) {
            NSLog(@"socket() failed: %s", strerror(errno));
            continue;
        }

        // configure the socket for broadcast mode
        int yes = 1;
        if (-1 == setsockopt(sock, SOL_SOCKET, SO_BROADCAST, &yes, sizeof yes)) {
            NSLog(@"setsockopt() failed: %s", strerror(errno));
        }

        // create some bytes to send
        NSString *message = @"Hello world!\n";
        NSData *data = [message dataUsingEncoding:NSUTF8StringEncoding];

        if (-1 == connect(sock, addr, addr->sa_len)) {
            NSLog(@"connect() failed: %s", strerror(errno));
        }

        // send the message
        ssize_t sent_bytes = send(sock, data.bytes, data.length, 0);
        if (sent_bytes == -1) {
            NSLog(@"send() failed: %s", strerror(errno));
        }
        else if (sent_bytes<data.length) {
            NSLog(@"send() sent only %d of %d bytes", (int)sent_bytes, (int)data.length);
        }

        // close the socket! important! there is only a finite number of file descriptors available!
        if (-1 == close(sock)) {
            NSLog(@"close() failed: %s", strerror(errno));
        }
    }

    freeifaddrs(interfaces);
}

此示例方法在端口16000上广播UDP消息.

This sample method broadcasts a UDP message on port 16000.

要进行调试，可以使用工具 socat .只需在您的计算机上运行以下命令(该命令应该与电话位于同一网络上)即可:

For debugging, you can use the tool socat. Just run the following command on your computer (which should be on the same network as the phone):

socat UDP-RECV:16000 STDOUT