iOS oc 组播

在 iOS 中，可以使用 MulticastSocket 实现组播功能。下面是一个基本的示例代码：

#import <UIKit/UIKit.h>
#import <arpa/inet.h>
#import <sys/socket.h>

@interface MulticastSocket : NSObject

@property (nonatomic, assign) int socketDescriptor;
@property (nonatomic, assign) struct sockaddr_in multicastAddr;

- (BOOL)joinMulticastGroup:(NSString *)multicastGroup onInterface:(NSString *)networkInterface;
- (BOOL)leaveMulticastGroup:(NSString *)multicastGroup onInterface:(NSString *)networkInterface;
- (BOOL)sendData:(NSData *)data toMulticastGroup:(NSString *)multicastGroup onPort:(int)port;

@end

@implementation MulticastSocket

- (BOOL)joinMulticastGroup:(NSString *)multicastGroup onInterface:(NSString *)networkInterface {
    // 创建 socket
    self.socketDescriptor = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
    if (self.socketDescriptor < 0) {
        NSLog(@"Failed to create socket");
        return NO;
    }
    
    // 设置 socket 选项
    int reuse = 1;
    if (setsockopt(self.socketDescriptor, SOL_SOCKET, SO_REUSEADDR, (char *)&reuse, sizeof(reuse)) < 0) {
        NSLog(@"Failed to set socket options");
        return NO;
    }
    
    // 绑定 socket
    struct sockaddr_in localAddr;
    memset((char *)&localAddr, 0, sizeof(localAddr));
    localAddr.sin_family = AF_INET;
    localAddr.sin_port = htons(0);
    localAddr.sin_addr.s_addr = htonl(INADDR_ANY);
    if (bind(self.socketDescriptor, (struct sockaddr *)&localAddr, sizeof(localAddr)) < 0) {
        NSLog(@"Failed to bind socket");
        return NO;
    }
    
    // 设置组播地址
    memset((char *)&self.multicastAddr, 0, sizeof(self.multicastAddr));
    self.multicastAddr.sin_family = AF_INET;
    self.multicastAddr.sin_port = htons(12345);
    if (inet_aton([multicastGroup UTF8String], &self.multicastAddr.sin_addr) == 0) {
        NSLog(@"Invalid multicast address");
        return NO;
    }
    
    // 加入组播组
    struct ip_mreq mreq;
    memset((char *)&mreq, 0, sizeof(mreq));
    mreq.imr_multiaddr.s_addr = self.multicastAddr.sin_addr.s_addr;
    mreq.imr_interface.s_addr = htonl(INADDR_ANY);
    if (setsockopt(self.socketDescriptor, IPPROTO_IP, IP_ADD_MEMBERSHIP, (char *)&mreq, sizeof(mreq)) < 0) {
        NSLog(@"Failed to join multicast group");
        return NO;
    }
    
    return YES;
}

- (BOOL)leaveMulticastGroup:(NSString *)multicastGroup onInterface:(NSString *)networkInterface {
    // 离开组播组
    struct ip_mreq mreq;
    memset((char *)&mreq, 0, sizeof(mreq));
    mreq.imr_multiaddr.s_addr = self.multicastAddr.sin_addr.s_addr;
    mreq.imr_interface.s_addr = htonl(INADDR_ANY);
    if (setsockopt(self.socketDescriptor, IPPROTO_IP, IP_DROP_MEMBERSHIP, (char *)&mreq, sizeof(mreq)) < 0) {
        NSLog(@"Failed to leave multicast group");
        return NO;
    }
    
    // 关闭 socket
    if (close(self.socketDescriptor) < 0) {
        NSLog(@"Failed to close socket");
        return NO;
    }
    
    return YES;
}

- (BOOL)sendData:(NSData *)data toMulticastGroup:(NSString *)multicastGroup onPort:(int)port {
    // 发送数据到组播组
    struct sockaddr_in destAddr;
    memset((char *)&destAddr, 0, sizeof(destAddr));
    destAddr.sin_family = AF_INET;
    destAddr.sin_port = htons(port);
    if (inet_aton([multicastGroup UTF8String], &destAddr.sin_addr) == 0) {
        NSLog(@"Invalid multicast address");
        return NO;
    }
    
    if (sendto(self.socketDescriptor, [data bytes], [data length], 0, (struct sockaddr *)&destAddr, sizeof(destAddr)) < 0) {
        NSLog(@"Failed to send data");
        return NO;
    }
    
    return YES;
}

@end

使用示例：

// 创建组播 socket
MulticastSocket *socket = [[MulticastSocket alloc] init];
if (![socket joinMulticastGroup:@"224.0.0.1" onInterface:nil]) {
    NSLog(@"Failed to join multicast group");
    return;
}

// 发送数据到组播组
NSString *message = @"Hello, multicast!";
NSData *data = [message dataUsingEncoding:NSUTF8StringEncoding];
if (![socket sendData:data toMulticastGroup:@"224.0.0.1" onPort:12345]) {
    NSLog(@"Failed to send data");
}

// 离开组播组
if (![socket leaveMulticastGroup:@"224.0.0.1" onInterface:nil]) {
    NSLog(@"Failed to leave multicast group");
}