sendto错误:无效参数

Question

我很难在套接字中使用sendto()函数

int main(int argc, const char * argv[]) {

    int acceptFd;
    struct sockaddr_in servaddr, cliaddr;
    char recieveBuf[512];
    char sendBuf[512];
    socklen_t cliLen;

    if(-1 == (acceptFd = socket(AF_INET,SOCK_DGRAM,0))) perror("socket() failed.\n");
    bzero(&servaddr, sizeof(servaddr));
    servaddr.sin_family = AF_INET;
    servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
    servaddr.sin_port = htons(6789);
    if(-1==bind(acceptFd,(struct sockaddr*)&servaddr,sizeof(servaddr))) perror("bind() failed.\n");


    bzero(&cliaddr, sizeof(cliaddr));

    while(1){


        if(recvfrom(acceptFd, recieveBuf, 512, 0, (struct sockaddr*) &cliaddr, &cliLen) == -1) {
            perror("recvfrom() failed");
            continue;
        }

        strcpy(sendBuf,"recieved\n");
        printf("%s\n",sendBuf);
        if(-1 == sendto(acceptFd,sendBuf, 512,0,(struct sockaddr*)&cliaddr,cliLen)){
            perror("sendto() failed");
            continue;
        }
    }
}

recvfrom()工作正常，但是每次调用sendto()时，错误处理都会输出如下：sendto() failed: Invalid argument

发送程序在这里：

#include "test.AcceptMessage.pb.h"
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>

int main(int argc, const char * argv[]) {



    int sendSocket;
    struct sockaddr_in cliaddr;
    char buf[512];
    if(-1 == (sendSocket = socket(AF_INET,SOCK_DGRAM,0))) perror("socket() failed.\n");
    bzero(&cliaddr, sizeof(cliaddr));
    cliaddr.sin_family = AF_INET;
    cliaddr.sin_addr.s_addr = inet_addr("127.0.0.1");
    cliaddr.sin_port = htons(6789);

    sendto(sendSocket,buf, 512,0,(
            struct sockaddr*)&cliaddr, sizeof(cliaddr));



    recvfrom(sendSocket,buf,512,0, nullptr, nullptr);
    printf("%s\n",buf);





    return 0;
}

那么这个代码有什么问题呢？

Answer 1

来自man recvfrom

在调用之前，应该将addrlen初始化为与src_addr关联的缓冲区大小。

因此，使用以下方法初始化cliLen变量：

socklen_t cliLen = sizeof(cliaddr);

Answer 2

您根本没有理由在这里使用recvfrom()和sendto()。是一个连接的插座。只需使用send()和recv().