C语言 套接字编程：sendto 总是以 errno 22 (EINVAL) 失败
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Socket programming: sendto always fails with errno 22 (EINVAL)
提问by dc.
I am always getting no bytes sent, with an errno of 22 (EINVAL, Invalid Argument) with this code. The destination_hostis set elsewhere and known to be valid, so I really don't see what is going on. MAXMSGSIZEis 1000. No errors, or warnings. I am compiling with -Wall -Werror -pedantic
我总是没有发送任何字节，此代码的 errno 为 22（EINVAL，无效参数）。将destination_host在其他地方设置和已知是有效的，所以我真的不明白什么是要去。 MAXMSGSIZE是 1000。没有错误或警告。我正在编译-Wall -Werror -pedantic
char *data_rec;
u_int data_len;
int sockfd;
uint16_t *ns;
struct sockaddr_in address;
struct sockaddr *addr;
char *ip;
int i;
int errno;
int bytes_sent;
data_len = MAXMSGSIZE;
data_rec = malloc(sizeof(char)*MAXMSGSIZE);
ns = malloc(MAXMSGSIZE*sizeof(uint16_t));
ip = malloc(MAXMSGSIZE*sizeof(char));
data_rec = "some random test stuff";
sockfd = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP);
if(sockfd<0) {
printf("socket() failed\n");
}
inet_ntop(AF_INET,destination_host->h_addr,ip,MAXMSGSIZE);
memset(&address, 0, sizeof(address));
address.sin_family = AF_INET;
address.sin_port = htons(theirPort);
address.sin_addr.s_addr = (unsigned long)ip;
addr = (struct sockaddr*)&address;
bind(sockfd,addr,sizeof(address));
/*Convert the message to uint16_t*/
for(i=0; i<MAXMSGSIZE; i++) {
ns[i] = htons(data_rec[i]);
}
/* send the message */
bytes_sent = sendto(sockfd, ns, data_len, MSG_DONTWAIT, addr, sizeof(addr));
if(bytes_sent == -1) {
printf("Error sending: %i\n",errno);
}
回答by nos
You're giving the wrong size for the address. addris really a struct sockaddr_in, not a struct sockaddr.
您为地址提供了错误的大小。addr真的是一个struct sockaddr_in，不是一个struct sockaddr。
Change the last parameter of sendto to sizeof(address)
把sendto的最后一个参数改成 sizeof(address)
回答by SimonJ
inet_ntopprobably isn't what you want - it converts from network(i.e. wire) format into presentationformat (i.e. "1.2.3.4"). Try:
inet_ntop可能不是您想要的 - 它从网络（即有线）格式转换为演示格式（即“1.2.3.4”）。尝试：
address.sin_addr.s_addr = *((unsigned long *)destination_host->h_addr);
回答by chao wang
You have:
你有：
bytes_sent = sendto(sockfd, ns, data_len, MSG_DONTWAIT, addr, sizeof(addr));
Because sizeof(addr) == 4(or 8), use sizeof(*addr).
因为sizeof(addr) == 4（或 8），使用sizeof(*addr).
