Ok, if you look at some of my previous questions, I've been working on getting a simple connection up and running with C sockets (I'm still fairly new to the whole networking aspect of an program, but everyone has to start somewhere, right?). I've included the code below that I have so far and when I execute it, I get no errors, but at the same time, I don't get the packet on the other end. By the way, I'm programming multicast sockets in objective-C and "msgStatus" is just a label in my GUI (it's hooked up correctly, so there's no problem there). I'm just not seeing where I'm going wrong. Could someone possibly help me or point me in the right direction? Thanks!
好吧,如果你看一下我以前的一些问题,我一直在努力获得一个简单的连接和运行C套接字(我仍然相当新的程序的整个网络方面,但每个人都必须从某个地方开始, 对?)。我已经包含了我到目前为止的代码,当我执行它时,我没有错误,但同时,我没有得到另一端的数据包。顺便说一句,我在Objective-C中编写多播套接字,而“msgStatus”只是我GUI中的一个标签(它连接正确,因此没有问题)。我只是没有看到我出错的地方。有人可能会帮助我或指出我正确的方向吗?谢谢!
#define MAX_LEN 1024 /* maximum string size to send */
#define MIN_PORT 1024 /* minimum port allowed */
#define MAX_PORT 65535 /* maximum port allowed */
#define MYPORT 5673 /* port we will be using for our multicast socket */
-(void)broadcastMessage {//(NSString*)msg {
NSLog(@"broadcastMessage - Stage 1");
NSString *msg = @"From Master";
mc_ttl = 3; // number of node hops the message is allowed to travel across the network
// define the port we will be using
mc_port = MYPORT;
/* create a socket for sending to the multicast address */
if ((sock = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP)) < 0) {
NSLog(@"ERROR: broadcastMessage - socket() failed");
return;
}
mc_addr.sin_family = AF_INET;
mc_addr.sin_addr.s_addr = inet_addr("225.0.0.37");
mc_addr.sin_port = htons(mc_port);
if (bind(sock, (struct sockaddr *) &mc_addr, sizeof(struct sockaddr_in)) < 0) {
NSLog(@"ERROR: bind not successful");
return;
}
NSLog(@"broadcastMessage - Stage 2");
/* set the TTL (time to live/hop count) for the send */
if ((setsockopt(sock, IPPROTO_IP, IP_MULTICAST_TTL, (void*) &mc_ttl, sizeof(mc_ttl))) < 0) {
NSLog(@"ERROR: broadcastMessage - setsockopt() failed");
return;
}
NSLog(@"broadcastMessage - Stage 3");
/* construct a multicast address structure - erase everything in the structure first*/
memset(&mc_addr, 0, sizeof(mc_addr));
// prepare the message to be sent
char send_str[MAX_LEN];
/* clear send buffer */
memset(send_str, 0, sizeof(send_str));
// convert the message to a C string to send
[msg getCString:send_str maxLength:MAX_LEN encoding:NSASCIIStringEncoding];
//while (fgets(send_str, MAX_LEN, stdin)) {
NSLog(@"broadcastMessage - Stage 4");
// send_len = strlen(send_str);
/* send string to multicast address */
if ((sendto(sock, send_str, sizeof(send_str), 0, (struct sockaddr *) &mc_addr, sizeof(mc_addr))) != sizeof(send_str)) {
NSLog(@"ERROR: broadcastMessage - sendto() sent incorrect number of bytes");
return;
}
NSLog(@"broadcastMessage - Stage 5");
/* clear send buffer */
memset(send_str, 0, sizeof(send_str));
NSLog(@"broadcastMessage - Stage 6");
close(sock);
}
-(void)listenForPackets {
listeningFlag_on = 1;
NSLog(@"listenForPackets - Stage 1");
if ((listeningSock = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP)) < 0) {
NSLog(@"ERROR: listenForPackets - socket() failed");
return; // make the method return an int instead of void and use this statement to check for errors
}
// set reuse port to on to allow multiple binds per host
if ((setsockopt(listeningSock, SOL_SOCKET, SO_REUSEADDR, &listeningFlag_on, sizeof(listeningFlag_on))) < 0) {
NSLog(@"ERROR: listenForPackets - setsockopt() failed");
return; // make the method return an int instead of void and use this statement to check for errors
}
NSLog(@"listenForPackets - Stage 2");
// construct a multicast address structure after erasing anything in the listeningmc_addr structure
memset(&listeningmc_addr, 0, sizeof(listeningmc_addr));
listeningmc_addr.sin_family = AF_INET;
listeningmc_addr.sin_addr.s_addr = htonl(INADDR_ANY);
listeningmc_addr.sin_port = htons(mc_port);
// bind multicast address to socket
if ((bind(listeningSock, (struct sockaddr *) &listeningmc_addr, sizeof(listeningmc_addr))) < 0) {
NSLog(@"ERROR: listenForPackets - bind() failed");
return; // make the method return an int instead of void and use this statement to check for errors
}
//******************************************************************************************************************************
//******************************************************************************************************************************
NSString *ipAddress = [[NSString alloc] initWithString:self.getIPAddress];
const char *tmp = [ipAddress UTF8String];
listeningMc_addr_str = tmp;
printf("%s\n", listeningMc_addr_str);
listeningMc_req.imr_multiaddr.s_addr = inet_addr("225.0.0.37");
listeningMc_req.imr_interface.s_addr = htonl(INADDR_ANY);
// send an ADD MEMBERSHIP message via setsockopt
if ((setsockopt(listeningSock, IPPROTO_IP, IP_ADD_MEMBERSHIP, (void*) &listeningMc_req, sizeof(listeningMc_req))) < 0) {
NSLog(@"ERROR: listenForPackets - setsockopt() failed");
int err = errno;
NSLog(@"errno - %i", err);
NSLog(@"Error = %s", strerror(err));
perror("ERROR");
return; // make the method return an int instead of void and use this statement to check for errors
}
NSLog(@"listenForPackets - Stage 3");
for (;;) { // loop forever
// clear the receive buffers & structs
memset(listeningRecv_str, 0, sizeof(listeningRecv_str));
listeningFrom_len = sizeof(listeningFrom_addr);
memset(&listeningFrom_addr, 0, listeningFrom_len);
// block waiting to receive a packet
if ((listeningRecv_len = recvfrom(listeningSock, listeningRecv_str, MAX_LEN, 0, (struct sockaddr*)&listeningFrom_addr, &listeningFrom_len)) < 0) {
NSLog(@"ERROR: listenForPackets - recvfrom() failed");
return; // make the method return an int instead of void and use this statement to check for errors
}
NSLog(@"listenForPackets - Stage 4");
NSString *tmpy = [[NSString alloc] initWithCString:listeningRecv_str encoding:NSASCIIStringEncoding];
msgStatus.text = tmpy;
NSLog(@"ERROR");
}
// received string
printf("Received %d bytes from %s: ", listeningRecv_len, inet_ntoa(listeningFrom_addr.sin_addr));
printf("%s", listeningRecv_str);
}
// send a DROP MEMBERSHIP message via setsockopt
if ((setsockopt(listeningSock, IPPROTO_IP, IP_DROP_MEMBERSHIP, (void*) &listeningMc_req, sizeof(listeningMc_req))) < 0) {
NSLog(@"ERROR: listenForPackets - setsockopt() failed");
//return 1; // make the method return an int instead of void and use this statement to check for errors
}
close(listeningSock);
NSLog(@"listenForPackets - Stage 5 - Complete");
}
Here is the code I'm using to extract my IP Address.
这是我用来提取我的IP地址的代码。
-(NSString *)getIPAddress {
NSString *address = @"error";
struct ifaddrs *interfaces; // = NULL;
struct ifaddrs *temp_addr; // = NULL;
int success = 0;
// retrieve the current interfaces - returns 0 on success
success = getifaddrs(&interfaces);
if (success == 0)
{
// Loop through linked list of interfaces
temp_addr = interfaces;
while(temp_addr != NULL)
{
if(temp_addr->ifa_addr->sa_family == AF_INET)
{
// Check if interface is en0 which is the wifi connection on the iPhone
if([[NSString stringWithUTF8String:temp_addr->ifa_name] isEqualToString:@"en0"])
{
// Get NSString from C String
address = [NSString stringWithUTF8String:inet_ntoa(((struct sockaddr_in *)temp_addr->ifa_addr)->sin_addr)];
}
}
temp_addr = temp_addr->ifa_next;
}
}
// Free memory
freeifaddrs(interfaces);
return address;
}
2 个解决方案
#1
In the listener, I think you need to set
在听众中,我认为你需要设置
listeningMc_req.imr_interface.s_addr = htonl(INADDR_ANY);
... since that is also the interface on which you bind the socket. Depending on whether you run everything on a single host, you might need to consider the loopback interface and binding to INADDR_ANY will do that.
...因为这也是绑定套接字的接口。根据您是否在单个主机上运行所有内容,您可能需要考虑环回接口,并且绑定到INADDR_ANY将执行此操作。
#2
Is there a router between you and your destination? If so, there's some work that needs to be done to tell the router that you want to subscribe to the feed as well as tell the router you will be sending the feed.
你和目的地之间有路由器吗?如果是这样,那么需要做一些工作来告诉路由器您要订阅订阅源以及告诉路由器您将发送订阅源。
I would start by tcpdump-ing the connection to make sure the packet is leaving your machine first.
我将从tcpdump-ing连接开始,以确保数据包首先离开您的机器。
#1
In the listener, I think you need to set
在听众中,我认为你需要设置
listeningMc_req.imr_interface.s_addr = htonl(INADDR_ANY);
... since that is also the interface on which you bind the socket. Depending on whether you run everything on a single host, you might need to consider the loopback interface and binding to INADDR_ANY will do that.
...因为这也是绑定套接字的接口。根据您是否在单个主机上运行所有内容,您可能需要考虑环回接口,并且绑定到INADDR_ANY将执行此操作。
#2
Is there a router between you and your destination? If so, there's some work that needs to be done to tell the router that you want to subscribe to the feed as well as tell the router you will be sending the feed.
你和目的地之间有路由器吗?如果是这样,那么需要做一些工作来告诉路由器您要订阅订阅源以及告诉路由器您将发送订阅源。
I would start by tcpdump-ing the connection to make sure the packet is leaving your machine first.
我将从tcpdump-ing连接开始,以确保数据包首先离开您的机器。