Question

我正在尝试从UDP广播中获取数据，但没有recvfrom函数的响应。连接，绑定，一切都很好。

广播会有问题吗？

无论如何我可以检查确切的错误吗？

#include <iostream>
using namespace std;
//#include <ServerSocket.h>
#include <cstring>      
#include <sys/socket.h> 
#include <netdb.h>      
#include <stdio.h>
#include <stdlib.h>

int main()
{

    enter code here
    int status;
    int socketfd;
    int enableMulticast = 1;         // Argument for set socket 

    struct addrinfo host_info;       // The struct that getaddrinfo() fills up with data.
    struct addrinfo *host_info_list; // Pointer to the to the linked list of host_info's.
    struct sockaddr_in socketAddr;
    unsigned char incomming_data_buffer[IN_LEN];
    socklen_t socklen;
    #ifndef IN_LEN    
    #define IN_LEN 4096
    #endif  

    memset(&host_info, 0, sizeof host_info);
    memset(&socketAddr, 0, sizeof(struct sockaddr_in));

    cout << "Setting up the structs..."  << endl;

    host_info.ai_family = AF_UNSPEC;     // IP version not specified. Can be both.
    host_info.ai_socktype = SOCK_DGRAM; // Use SOCK_STREAM for TCP or SOCK_DGRAM for UDP.
    host_info.ai_protocol = IPPROTO_UDP; // The protocol type for UDP. If left as zero, it will return all types


    status = getaddrinfo("UDP IP Address","Port", &host_info, &host_info_list);

    socketfd = socket(host_info_list->ai_family, host_info_list->ai_socktype,
                      host_info_list->ai_protocol);
    if (socketfd == -1)  cout << "socket error " ;
    else cout << "socket created successfully " ;

    status = setsockopt(socketfd, SOL_SOCKET, SO_REUSEADDR, &enableMulticast, sizeof(enableMulticast));

    socketAddr.sin_family = AF_INET;
    socketAddr.sin_port = htons(INT_PORT);
    socketAddr.sin_addr.s_addr = htonl(INADDR_ANY);

    status = bind(socketfd, (struct sockaddr *)&socketAddr, sizeof(struct sockaddr_in));    

    status = connect(socketfd, host_info_list->ai_addr, host_info_list->ai_addrlen);
    if (status < 0)  cout << "connect error" <<endl ;

    cout << "Waiting to receive data..."  << endl;
    socklen = sizeof(struct socketAddr);

    while(1){
        status = recvfrom(socketfd, incomming_data_buffer, IN_LEN, 0, (struct sockaddr *)&socketAddr, &socklen);

        if(status >= 0) {
            cout << "data received" ;
            freeaddrinfo(host_info_list);
            close(socketfd);

            exit(0);
         }
    }     
}

Answer 1

if(status = 0)

这永远不会成真。（1）它是status == 0的拼写错误; （2）它应该是status >= 0，即status是收到的数据报的长度。

套接字连接recvfrom无响应C ++

1 个答案: