目前我是团队中唯一一个懂 C++ 语言的人。因此，我负责为我们已经存在的（可穿戴）Web 应用程序创建本机 tizen 服务。
该服务的主要目的是接收 UDP 消息，这些消息从同一网络内的系统广播（即连接到同一接入点）。
我制作了 2 个简单的 python 脚本。第一个在按钮点击时发送广播消息：
class UDPServer(object):
'''
A simple UDP server with a send method.
'''
def __init__(self):
'''
Initializes the server.
'''
import socket
self.socket = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
self.socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
self.socket.setsockopt(socket.SOL_SOCKET, socket.SO_BROADCAST, 1)
def broadcast_message(self, message):
'''
Sends out a broadcast message.
'''
self.socket.sendto(message, ('<broadcast>', 3333))
class GUI(object):
'''
A simple UI to use the server with.
'''
def __init__(self):
'''
Initializes the simple ui.
'''
import Tkinter
self.root = Tkinter.Tk()
self.root.title("UDP System")
self.button = Tkinter.Button(self.root, text="Action!")
self.button.place(x=0, y=0)
self.button.pack(fill='x')
self.root.update()
def action(self, callback, *args):
'''
Sets the action to be performed when the button's being called.
'''
self.button.configure(command=lambda: callback(*args))
def run(self):
'''
Invokes the message pump of the root widget.
'''
self.root.mainloop()
def main():
'''
Launches the UDP server and its ui.
'''
server = UDPServer()
gui = GUI()
gui.action(server.broadcast_message, "Hello, World!")
gui.run()
if __name__ == '__main__':
main()
后者接收这些消息：
class GUI(object):
'''
Simple GUI for the receiver.
'''
def __init__(self):
'''
Initializes the UI.
'''
import Tkinter
self.root = Tkinter.Tk()
self.root.title("UDPReceiver")
self.list = Tkinter.Listbox(self.root)
self.list.pack(fill='x')
def add_message(self, message):
'''
Adds an message to the listbox.
'''
self.list.insert(0, message)
def run(self):
'''
Runs the widgets mainloop.
'''
self.root.mainloop()
class Receiver(object):
'''
Simple UDP receiver.
'''
def __init__(self):
'''
Initializes a simple udp receiver/client.
'''
import socket
self.socket = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
self.socket.bind(('', 3333))
def recv(self):
'''
Listens for a message and returns it.
'''
return self.socket.recvfrom(4096)
def main():
'''
Launches the udp receiver and its ui.
'''
gui = GUI()
client = Receiver()
def proc():
'''
A simple fetch and update routine to be run
in a seperate thread.
'''
while gui.root.state() == 'normal':
msg = client.recv()
gui.add_message(msg)
from thread import start_new_thread
start_new_thread(proc, ())
gui.run()
if __name__ == '__main__':
main()
显然这两个脚本都正常工作，因为我能够接收到另一个脚本发出的消息（但是，仅在同一台 PC 上对其进行了测试。）
现在我正在尝试为本机服务实现“侦听行为”。该应用程序似乎工作正常，没有崩溃。然而它没有收到任何东西，尽管下面的代码看起来不错：
UDPSocket::UDPSocket()
: socket{0}
{
addrinfo hints{0, };
const char* pHostname = 0;
const char* pPortname = "3333";
hints.ai_family = AF_UNSPEC;
hints.ai_family = SOCK_DGRAM;
hints.ai_protocol = 0;
hints.ai_flags = AI_PASSIVE | AI_ADDRCONFIG;
addrinfo* res{nullptr};
int err = ::getaddrinfo(pHostname, pPortname, &hints, &res);
if(0 != err){
throw std::runtime_error{"Failed to get address info."};
}
socket = ::socket(res->ai_family, res->ai_socktype, res->ai_protocol);
if(-1 == socket){
throw std::runtime_error{"Failed to create socket."};
}
int broadcast = 1;
::setsockopt(socket, SOL_SOCKET, SO_BROADCAST, &broadcast, sizeof(broadcast));
err = ::bind(socket, res->ai_addr, res->ai_addrlen);
if(-1 == err){
throw std::runtime_error{"Failed to bind socket."};
}
freeaddrinfo(res);
}
UDPSocket::~UDPSocket()
{
close(socket);
}
std::string UDPSocket::listen() const{
char buffer[512];
sockaddr_storage src_addr;
socklen_t src_addr_len = sizeof(src_addr);
ssize_t count = ::recvfrom(socket,
buffer,
sizeof(buffer),
0,
(sockaddr*) &src_addr,
&src_addr_len);
if(-1 == count){
throw std::runtime_error{strerror(errno)};
} else if (count == sizeof(buffer)){
// Issue warning
return buffer;
} else{
return buffer;
}
}
应用程序在模拟器中运行良好，除了调用“UDPSocket::listen()”时服务停止的事实——我想这是因为我处于阻塞模式。无论我多久点击一次发送按钮，它都会停止并且永远不会收到任何东西，这会用 UDP 消息淹没我的本地网络。
TL;DR 在 Tizen 模拟器上接收 UDP 消息是否需要任何特殊的配置步骤？
奖励问题：我想要一种方法来持续注意传入的 UDP 消息。我应该为服务中的“接收者”启动一个额外的线程吗？