c++ - 服务器 UDP 函数 recvfrom

Question

我写了下面的代码，实现了在 Linux 中工作的服务器 UDP，C++，这是出错的相关部分:

#include<iostream>
#include<arpa/inet.h>
#include<unistd.h>
#include<sys/socket.h>
#include<sys/types.h>
#include<stdio.h>
#include<string.h>
#include<stdlib.h>
#include<netinet/in.h>
#include <sys/types.h>
#include <sys/socket.h>
using namespace std;


int main()
{
  int welcomeSocket,newSocket,nBytes;
  struct sockaddr_in serverAddr;
  struct sockaddr_in remaddr;
  char buffer[1024];
  socklen_t addrlen;

  welcomeSocket=socket(AF_INET,SOCK_DGRAM,0);
  if(welcomeSocket<0)
  {
    cout<<"Errr"<<endl;
  }
  else
  {
    cout<<"succes"<<endl;
    serverAddr.sin_family=AF_INET;
    serverAddr.sin_port=htons(7891);
    serverAddr.sin_addr.s_addr=inet_addr("127.0.0.1");
    if(bind(welcomeSocket,(struct sockaddr*)&serverAddr,sizeof(serverAddr))<0)
    {
        cout<<"bind failed"<<endl;
        return 0;
    }
    else
    {
        addrlen=sizeof(remaddr);
        while(1)
        {
            cout<<"Waiting on port 7891"<<endl;
            recvfrom(welcomeSocket,buffer,1024,0,(struct sockaddr_in*)&remaddr,(socklen_t*)&addrlen);

        }
    }

}
}

但是当我使用 make 编译时，我得到一个关于函数 recvfrom 的错误，我遇到的错误是:

invalid conversion from ‘int’ to ‘void*’ [-fpermissive]
invalid conversion from ‘sockaddr_in*’ to ‘int’ [-fpermissive]
cannot convert ‘socklen_t* {aka unsigned int*}’ to ‘sockaddr*’ for  argument ‘5’ to ‘ssize_t recvfrom(int, void*, size_t, int, sockaddr*, socklen_t*)’

怎么了，我不明白。

Answer 1

添加缺少的 buffer 参数后，问题出在第五个参数上:

(struct sockaddr_in*)&remaddr

它需要一个struct sockaddr *:

recvfrom(welcomeSocket,buffer,1024,0,(struct sockaddr *)&remaddr,(socklen_t *)&addrlen);