Websockets使用asio c库作为服务器并使用javascript作为客户端
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我已经使用asio库用C语言编写了服务器代码.我知道服务器代码可以正常工作,因为我是用同样用C编写并使用asio的客户端对其进行测试的.
问题在于,使用以下用于客户端的javascript代码时,连接不会被接受.我立即在javascript客户端上看到消息连接已关闭…,在服务器上,我看到以下奇怪消息：
Data RECEIVED: <------ I print this line myself
GET / HTTP/1.1
Host: localhost:15562
Connection: Upgrade
Pragma: no-cache
Cache-Control: no-cache
Upgrade: websocket
Origin: http://localhost:63344
Sec-WebSocket-Version: 13
User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/49.0.2623.110 Safari/537.36
Accept-Encoding: gzip, deflate, sdch
Accept-Language: en-US,en;q=0.8
Sec-WebSocket-Key: IidMJmdoGe4kYu0+1VlrvQ==
Sec-WebSocket-Extensions: permessage-deflate; client_max_window_bits
index.html-连接立即关闭…几乎与here相同的代码
function WebSocketTest() {
if ("WebSocket" in window) {
var ws = new WebSocket("ws://localhost:15562");
ws.onopen = function () {
alert("Connection opened...");
};
ws.onmessage = function (evt) {
alert("Message received...");
};
ws.onclose = function () {
alert("Connection closed...");
};
ws.send("Hi, from the client");
ws.send("Hi, from the client");
}
}
server.cpp-正常工作.几乎与here相同的代码
#define ASIO_STANDALONE
#include <iostream>
#include <asio.hpp>
using asio::ip::tcp;
const std::size_t max_length = 2048;
const unsigned short PORT = 15562;
class Session
: public std::enable_shared_from_this<Session>
{
public:
Session(tcp::socket server_socket)
: _session_socket(std::move(server_socket))
{
}
void start()
{
do_read();
}
private:
void do_read()
{
auto self(shared_from_this()); // shared_ptr instance to this
// Start an asynchronous read.
// This function is used to asynchronously read data from the stream socket.
_session_socket.async_read_some(asio::buffer(_data, max_length),
[this, self](std::error_code error, std::size_t length)
{
if (!error)
{
std::cout << "Data RECEIVED: " << std::endl;
std::cout << _data << std::endl;
do_write(length);
}
});
}
void do_write(std::size_t length)
{
auto self(shared_from_this()); // shared_ptr instance to this
// Start an asynchronous write.
// This function is used to asynchronously write data to the stream socket.
strncpy(_data, "Hi, from the server", max_length);
asio::async_write(_session_socket, asio::buffer(_data, length),
[this, self](std::error_code error, std::size_t /*length*/)
{
if (!error)
{
do_read();
}
});
}
tcp::socket _session_socket;
char _data[max_length];
};
class server
{
public:
server(asio::io_service &io_service, const tcp::endpoint &endpoint)
: _server_socket(io_service),
_server_acceptor(io_service, endpoint)
{
}
void do_accept()
{
// Start an asynchronous accept.
// This function is used to asynchronously accept a new connection into a socket.
_server_acceptor.async_accept(_server_socket,
[this](std::error_code error)
{
// Accept succeeded
if (!error)
{
// Create a session
auto session = std::make_shared<Session>(
std::move(_server_socket));
session->start();
}
// Continue to accept more connections
do_accept();
});
}
private:
tcp::acceptor _server_acceptor;
tcp::socket _server_socket;
};
int main()
{
try
{
asio::io_service io_service; // io_service provides functionality for sockets, connectors, etc
tcp::endpoint endpoint(tcp::v4(), PORT); // create an endpoint using a IP='any' and the specified PORT
server server(io_service, endpoint); // create server on PORT
server.do_accept();
std::cout << "Server started on port: " << PORT << std::endl;
io_service.run();
}
catch (std::exception &e)
{
std::cerr << "Exception: " << e.what() << "\n"; // Print error
}
return 0;
}
client.cpp-正常工作.几乎与here相同的代码
#define ASIO_STANDALONE
#include <iostream>
#include <asio.hpp>
using asio::ip::tcp;
int main(int argc, char *argv[])
{
asio::io_service io_service;
tcp::socket socket(io_service);
tcp::resolver resolver(io_service);
// Connect
asio::connect(socket, resolver.resolve({"localhost", "15562"}));
for (int i = 0; i < 10; ++i)
{
std::cout << "Enter message to sent to server:" << std::endl;
char client_message[2048];
std::cin.getline(client_message, 2048);
// Send message to server
asio::write(socket, asio::buffer(client_message, 2048));
char server_message[2048];
// Read message from server
asio::read(socket, asio::buffer(server_message, 2048));
std::cout << "Reply is: " << std::endl;
std::cout << server_message << std::endl;
}
return 0;
}
解决方法:
您的javascript代码正在发送您指向的标头并等待标头,例如：
HTTP/1.1 101 Switching Protocols
Upgrade: websocket
Connection: Upgrade
Sec-WebSocket-Accept: 5A4gqmvwM2kbopObEm+Kr6zBrNw=
Sec-WebSocket-Protocol: echo-protocol
但是,您发送回已经得到的相同标头.这是不正确的.因此,您将获得“连接已关闭…”.
您应该使Sec-WebSocket-Accept的标头具有正确的值.
例如,do_write方法可能看起来
void do_write(std::size_t length)
{
auto self(shared_from_this());
std::stringstream handshake;
std::string tmp(data_);
tmp.erase(0, tmp.find("Sec-WebSocket-Key: ") + strlen("Sec-WebSocket-Key: "));
auto key = tmp.substr(0, tmp.find("\r\n"));
auto sha1 = SimpleWeb::Crypto::SHA1(key + ws_magic_string);
handshake << "HTTP/1.1 101 Switching Protocols\r\n";
handshake << "Upgrade: websocket\r\n";
handshake << "Connection: Upgrade\r\n";
handshake << "Sec-WebSocket-Accept: " << SimpleWeb::Crypto::Base64::encode(sha1) << "\r\n";
handshake << "Sec-WebSocket-Protocol: echo-protocol\r\n";
handshake << "\r\n";
boost::asio::async_write(socket_, boost::asio::buffer(handshake.str().c_str(), handshake.str().size()),
[this, self](boost::system::error_code ec, std::size_t /*length*/)
{
if (!ec)
{
do_read();
}
});
}
在这里,我使用了项目https://github.com/eidheim/Simple-WebSocket-Server中的Crypto方法,其中将ws_magic_string定义为
const std::string ws_magic_string = "258EAFA5-E914-47DA-95CA-C5AB0DC85B11";
祝好运.
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