此代码与原始 udp 异步回显服务器相同,但具有不同的套接字。
响应已传输并显示在wireshark 中,但随后会向服务器发送回ICMP 端口不可达错误。我试图理解为什么,因为一切看起来都是正确的。
您可以将此代码直接复制到源文件中,例如服务器.cpp。然后编译
gcc server.cpp -lboost_system
使用如下命令运行它:./a.out 35200
#include <cstdlib>
#include <iostream>
#include <boost/bind.hpp>
#include <boost/asio.hpp>
using boost::asio::ip::udp;
class server
{
public:
server(boost::asio::io_service& io_service, short port)
: io_service_(io_service),
socket_(io_service, udp::endpoint(udp::v4(), port)),
socket2_(io_service, udp::endpoint(udp::v4(),0))
{
socket_.async_receive_from(
boost::asio::buffer(data_, max_length), sender_endpoint_,
boost::bind(&server::handle_receive_from, this,
boost::asio::placeholders::error,
boost::asio::placeholders::bytes_transferred));
}
void handle_receive_from(const boost::system::error_code& error,
size_t bytes_recvd)
{
if (!error && bytes_recvd > 0)
{
// use a different socket... random source port.
socket2_.async_send_to(
boost::asio::buffer(data_, bytes_recvd), sender_endpoint_,
boost::bind(&server::handle_send_to, this,
boost::asio::placeholders::error,
boost::asio::placeholders::bytes_transferred));
}
else
{
socket_.async_receive_from(
boost::asio::buffer(data_, max_length), sender_endpoint_,
boost::bind(&server::handle_receive_from, this,
boost::asio::placeholders::error,
boost::asio::placeholders::bytes_transferred));
}
}
void handle_send_to(const boost::system::error_code& /*error*/,
size_t /*bytes_sent*/)
{
// error_code shows success when checked here. But wireshark shows
// an ICMP response with destination unreachable, port unreachable when run on
// localhost. Haven't tried it across a network.
socket_.async_receive_from(
boost::asio::buffer(data_, max_length), sender_endpoint_,
boost::bind(&server::handle_receive_from, this,
boost::asio::placeholders::error,
boost::asio::placeholders::bytes_transferred));
}
private:
boost::asio::io_service& io_service_;
udp::socket socket_;
udp::socket socket2_;
udp::endpoint sender_endpoint_;
enum { max_length = 1024 };
char data_[max_length];
};
int main(int argc, char* argv[])
{
try
{
if (argc != 2)
{
std::cerr << "Usage: async_udp_echo_server <port>\n";
return 1;
}
boost::asio::io_service io_service;
using namespace std; // For atoi.
server s(io_service, atoi(argv[1]));
io_service.run();
}
catch (std::exception& e)
{
std::cerr << "Exception: " << e.what() << "\n";
}
return 0;
}
我需要这个的原因是因为我有多个线程从由 UDP 服务器提供的输入队列接收数据。现在我希望这些线程能够直接发送响应,但我无法让它工作。
如果我在 async_send_to 调用中使用原始套接字(即 socket_),那么它就可以工作。
好的...这是测试客户端,它不适用于上面的代码(但适用于 asio 示例中的原始版本)。
#!/usr/bin/python
import socket, sys, time, struct
textport = "35200"
host = "localhost"
if len(sys.argv) > 1:
host = sys.argv[1]
print "Sending Data"
s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
port = int(textport)
s.connect((host, port))
s.sendall("Hello World")
#s.shutdown(1)
print "Looking for replies; press Ctrl-C or Ctrl-Break to stop."
while 1:
buf = s.recv(1200)
if not len(buf):
break
print "Received: %s" % buf
让我很困惑。但至少我可以使用 C++ UDP 客户端并且它可以工作。