TCP/IP UDP广播无法发送或者接收数据
在看《TCP/IP 网络编程》这本书的时候,看到广播那一节,跟着书上写代码,怎么写都不行,广播就是没法发送/接收,发送端一直在发送数据,接收端就是没有反应。
对了好几遍源码,没有问题。实在是愁人。
最后查了很多资料,确定是网卡的问题。
现在的计算机都是多网卡,至少是有线+无线网卡,如果安装了虚拟机的话,还会有虚拟网卡。
广播地址无法区分网卡,只能按照默认网卡优先级发送,这就导致我们的数据没有走那个我们需要的网卡发送出去。进而导致收不到数据。
解决办法
- 禁用一些网卡,将用不到的网卡全部禁用掉
- 在代码里添加绑定IP地址的逻辑,绑定到具体的网卡IP
我是用的是第2种方式,比较方便灵活。
发送端Linux源码:
#include <arpa/inet.h>
#include <asm-generic/socket.h>
#include <cstdio>
#include <cstring>
#include <fstream>
#include <iostream>
#include <iterator>
#include <linux/in.h>
#include <sys/endian.h>
#include <sys/socket.h>
#include <unistd.h>
#ifndef FILEPATH
#define FILEPATH "../news.txt"
#endif
constexpr int BUF_SIZE = 30;
int main(int argc, char* argv[])
{
if (argc != 4) {
std::cout << "Usage: " << argv[0] << "<Self IP> <Boardcast IP> <PORT>" << std::endl;
return 0;
}
int send_socket = socket(PF_INET, SOCK_DGRAM, 0);
// 绑定到具体的网卡IP
sockaddr_in self_adr;
std::memset(&self_adr, 0, sizeof(self_adr));
self_adr.sin_family = AF_INET;
self_adr.sin_addr.s_addr = inet_addr(argv[1]);
self_adr.sin_port = 0; // 随机分配一个端口
int res = bind(send_socket, (sockaddr*)&self_adr, sizeof(self_adr));
if (res == -1) {
std::cout << "bind error";
}
sockaddr_in broad_adr;
std::memset(&broad_adr, 0, sizeof(broad_adr));
broad_adr.sin_family = AF_INET;
broad_adr.sin_addr.s_addr = inet_addr(argv[2]);
broad_adr.sin_port = htons(std::atoi(argv[3]));
int so_brd = 1;
int rtn = setsockopt(send_socket, SOL_SOCKET, SO_BROADCAST, &so_brd, sizeof(so_brd));
if (rtn == -1) {
std::cout << "setsockopt error" << std::endl;
return 0;
}
std::ifstream fi { FILEPATH };
while (!fi.eof()) {
std::string msg;
fi >> msg;
int s = sendto(send_socket, msg.c_str(), msg.size(), 0, (sockaddr*)&broad_adr, sizeof(broad_adr));
std::cout << s << ":" << msg << std::endl;
sleep(2);
}
close(send_socket);
return 0;
}
接收端Linux源码:文章来源:https://www.toymoban.com/news/detail-763660.html
#include <arpa/inet.h>
#include <cstring>
#include <iostream>
#include <linux/in.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <unistd.h>
constexpr int BUF_SIZE = 30;
int main(int argc, char* argv[])
{
if (argc != 2) {
std::cout << "Usage: " << argv[0] << " <PORT>" << std::endl;
return 0;
}
int recv_sock = socket(PF_INET, SOCK_DGRAM, 0);
sockaddr_in adr;
std::memset(&adr, 0, sizeof(adr));
adr.sin_family = AF_INET;
adr.sin_addr.s_addr = htonl(INADDR_ANY);
int port = std::atoi(argv[1]);
adr.sin_port = htons(port);
std::cout << "PORT: " << port << std::endl;
int rtn = bind(recv_sock, (sockaddr*)&adr, sizeof(adr));
if (rtn == -1) {
std::cout << "bind error" << std::endl;
return 0;
}
char buf[BUF_SIZE] = { 0 };
while (true) {
sockaddr_in src_adr;
socklen_t sl = 0;
int l = recvfrom(recv_sock, buf, BUF_SIZE - 1, 0, (sockaddr*)&src_adr, &sl);
std::string srcIp = inet_ntoa(src_adr.sin_addr);
std::cout << srcIp << " - ";
if (l < 0) {
break;
}
buf[l] = 0;
std::cout << buf;
}
close(recv_sock);
return 0;
}
接收端Win源码:文章来源地址https://www.toymoban.com/news/detail-763660.html
#include <WS2tcpip.h>
#include <WinSock2.h>
#include <cstdlib>
#include <cstring>
#include <iostream>
constexpr int BUF_SIZE = 30;
int main(int argc, char* argv[])
{
if (argc != 2) {
std::cout << "Usage: " << argv[0] << " <PORT>" << std::endl;
return 0;
}
WSADATA wsaData;
if (WSAStartup(MAKEWORD(2, 2), &wsaData) != 0) {
std::cout << "WSA error" << std::endl;
return 0;
}
SOCKET recvSock = socket(PF_INET, SOCK_DGRAM, 0);
SOCKADDR_IN adr;
std::memset(&adr, 0, sizeof(adr));
adr.sin_family = AF_INET;
adr.sin_addr.s_addr = htonl(INADDR_ANY);
int port = std::atoi(argv[1]);
adr.sin_port = htons(port);
int rtn = bind(recvSock, (SOCKADDR*)&adr, sizeof(adr));
if (rtn == SOCKET_ERROR) {
std::cout << "bind error" << std::endl;
return 0;
}
std::cout << "服务已启动:" << port << std::endl;
char buf[BUF_SIZE] = { 0 };
while (true) {
int strLen = recvfrom(recvSock, buf, BUF_SIZE - 1, 0, nullptr, 0);
if (strLen < 0) {
break;
}
buf[strLen] = 0;
std::cout << buf << std::endl;
}
closesocket(recvSock);
WSACleanup();
return 0;
}
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