我正在尝试构建一个非常简单且基本的STCP一对多服务器以进行测试,但是由于某种原因,套接字似乎只能接收一条消息。收到一条消息后,对recvmsg
的每个后续调用均返回-1,且errno
为EFAULT
。这对我来说绝对没有意义,所以也许您可以告诉我我在这里没看到的内容。 EFAULT
应该在以下情况下返回
EFAULT
The receive buffer pointer(s) point outside the process's address space.
绝对不是这样。
#include <ctype.h>
#include <cstring>
#include <stdio.h>
#include <iostream>
#include <unistd.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <netinet/in.h>
int main(int argc, char** argv) {
struct sockaddr_in bind_address;
bind_address.sin_family = AF_INET;
bind_address.sin_port = htons(51338);
bind_address.sin_addr.s_addr = INADDR_ANY;
int sock = socket(AF_INET, SOCK_SEQPACKET, IPPROTO_SCTP);
if (sock == -1) {
perror("Error while creating socket");
return 1;
}
int rv = bind(sock, (struct sockaddr*)(&bind_address), sizeof(bind_address));
if (rv != 0 ) {
perror("Error while binding socket");
return 1;
}
rv = listen(sock, 1);
if (rv != 0 ) {
perror("Error while listening");
return 1;
}
struct iovec iov[1];
iov[0].iov_base = malloc(1500);
iov[0].iov_len = 1500;
struct sockaddr_in sin = {};
char control[1000] = { 0 };
struct msghdr mhdr;
mhdr.msg_iov = iov;
mhdr.msg_iovlen = sizeof(iov);
mhdr.msg_name = &sin;
mhdr.msg_namelen = sizeof(sin);
mhdr.msg_control = &control;
mhdr.msg_controllen = sizeof(control);
while (true) {
std::memset(iov[0].iov_base, 0, iov[0].iov_len);
std::memset(&sin, 0, sizeof(sin));
int recv_bytes = recvmsg(sock, &mhdr, 0);
if (recv_bytes == -1) {
if (errno == EAGAIN || errno == EWOULDBLOCK) {
continue;
} else {
perror("Err");
}
break;
}
std::cout << "Received message: " << std::endl;
std::cout << (char*)iov[0].iov_base << std::endl;
}
return 0;
}
最佳答案
该错误最有可能是因为第一次调用recvmsg()
会覆盖堆栈上的某些数据,从而导致mhdr
内部的一个指针无效。这可能是因为以下这一行:
mhdr.msg_iovlen = sizeof(iov);
它不应包含iov
数组的大小(以字节为单位),而应包含该数组中元素的数量,因此:mhdr.msg_iovlen = sizeof(iov) / sizeof(*iov); // which equals 1 in this case
关于c++ - SCTP recvmsg返回EFAULT(错误地址),我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/64282046/