blocks|key|4142568|text|对于未到达目的地的UDP数据包，您永远不会收到错误或通知。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4142569|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

You can never receive an error, or notice for a UDP packet that did not reach destination.

blocks|key|76226|text|sendto调用没有失败。数据报已发送到目的地。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|76227|数据报的接收方或途中的某个路由器可能会返回错误响应(主机无法到达、端口无法到达、超过TTL+)。但是当您的系统收到sendto调用时，它将成为历史记录。有些操作系统确实提供了一种方法来找出发生这种情况的原因，通常是通过getsockopt调用。但是，由于您不能依赖于获得错误回复，因为它取决于您无法控制的网络条件，因此通常最好忽略它。|76228|位于UDP之上的合理协议使用应答。如果你没有得到回复，那么要么是另一端没有收到你的数据报，要么是回复没有发回给你。|76229|entityMap^0|0|6|0|1L|6|31|A|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@$9|M|A|N|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|O|8|@$9|P|A|Q|B|C]|$9|R|A|S|B|C]]|D|@]|E|$]]|$1|H|3|I|5|6|7|T|8|@]|D|@]|E|$]]|$1|J|3|-4|5|6|7|U|8|@]|D|@]|E|$]]]|K|$]]

The <code>sendto</code> call didn't fail. The datagram was sent to the destination.

The recipient of the datagram or some router on the way to it might return an error response (host unreachable, port unreachable, TTL exceeded). But the <code>sendto</code> call will be history by the time your system receives it. Some operating systems do provide a way to find out this occurred, often with a <code>getsockopt</code> call. But since you can't rely on getting an error reply anyway since it depends on network conditions you have no control over, it's generally best to ignore it.

Sensible protocols layered on top of UDP use replies. If you don't get a reply, then either the other end didn't get your datagram or the reply didn't make it back to you.

blocks|key|906594|text|type|unstyled|depth|inlineStyleRanges|entityRanges|data|906595|+"UDP是一种更简单的基于消息的无连接协议。在无连接协议中，不需要建立专用的端到端连接。通信是通过在单向中传输信息来实现的，从源到目的地，无需检查目的地是否还在那里，或者它是否准备接收信息。“|blockquote|offset|length|style|BOLD|906596|906597|entityMap^0|0|1F|2|0|0^^$0|@$1|2|3|-4|4|5|6|K|7|@]|8|@]|9|$]]|$1|A|3|B|4|C|6|L|7|@$D|M|E|N|F|G]]|8|@]|9|$]]|$1|H|3|-4|4|5|6|O|7|@]|8|@]|9|$]]|$1|I|3|-4|4|5|6|P|7|@]|8|@]|9|$]]]|J|$]]

<blockquote>
 "UDP is a simpler message-based connectionless protocol. In connectionless protocols, there is no effort made to set up a dedicated end-to-end connection. Communication is achieved by transmitting information in one direction, from source to destination without checking to see if the destination is still there, or if it is prepared to receive the information."
</blockquote>

blocks|key|906632|text|您要向其发送数据包的机器可能会回复ICMP+UDP端口无法到达消息。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|906633|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

The machine to which you're sending packets may reply with an ICMP UDP port unreachable message.

blocks|key|75878|text|UDP协议是在IP之上实现的。将UDP数据包发送到由IP地址标识的主机，而不是MAC地址。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|75879|正如所指出的，UDP本身不会发送回复，您必须自己添加代码来完成此操作。然后，您将必须添加代码以等待响应，并在响应丢失时采取适当的操作(通常在计时器上重新发送，直到您确定另一端是“死”的)，依此类推。|75880|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

The UDP protocol is implemented on top of IP. You send UDP packets to hosts identified by IP addresses, not MAC addresses.

And as pointed out, UDP itself will not send a reply, you will have to add code to do that yourself. Then you will have to add code to expect the reply, and take the proper action if the response is lost (typically resend on a timer, until you decide the other end is "dead"), and so on.

blocks|key|4142714|text|如果您需要可靠的UDP，例如在订购或验证时，TCP/IP将为您提供RUDP或可靠的UDP。有时您确实需要验证，但是UDP和TCP的混合可能会阻碍TCP的可靠性，从而导致瓶颈。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4142715|对于大多数大规模的MMO来说，UDP和可靠性UDP是通信和可靠性的手段。RUDP所做的就是添加一小部分TCP/IP来验证和排序某些消息，但不是全部。|4142716|一个常见的游戏开发网络库是Raknet，它内置了这个。|4142717|RUDP+http://www.javvin.com/protocolRUDP.html|offset|length|4142718|使用Raknet和Python+http://pyraknet.slowchop.com/的RUDP示例|4142719|entityMap|0|LINK|mutability|MUTABLE|url|http://www.javvin.com/protocolRUDP.html|1|http://pyraknet.slowchop.com/^0|0|0|0|5|13|0|0|G|T|1|0^^$0|@$1|2|3|4|5|6|7|V|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|W|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|X|8|@]|9|@]|A|$]]|$1|F|3|G|5|6|7|Y|8|@]|9|@$H|Z|I|10|1|11]]|A|$]]|$1|J|3|K|5|6|7|12|8|@]|9|@$H|13|I|14|1|15]]|A|$]]|$1|L|3|-4|5|6|7|16|8|@]|9|@]|A|$]]]|M|$N|$5|O|P|Q|A|$R|S]]|T|$5|O|P|Q|A|$R|U]]]]

If you need reliable UDP as in ordering or verification such that TCP/IP will give you take a look at RUDP or Reliable UDP. Sometimes you do need verification but a mixture of UDP and TCP can be held up on the TCP reliability causing a bottleneck.

For most large scale MMO's for isntance UDP and Reliablity UDP are the means of communication and reliability. All RUDP does is add a smaller portion of TCP/IP to validate and order certain messages but not all.

A common game development networking library is Raknet which has this built in.

RUDP
<a href="http://www.javvin.com/protocolRUDP.html" rel="nofollow noreferrer">http://www.javvin.com/protocolRUDP.html</a>

An example of RUDP using Raknet and Python
<a href="http://pyraknet.slowchop.com/" rel="nofollow noreferrer">http://pyraknet.slowchop.com/</a>

UDP doesnot sends any ack back, but will it send any response?

I have set up client server UDP program. If I give client to send data to non existent server then will client receive any response?

My assumption is as;

Client -->Broadcast server address (ARP)
Server --> Reply to client with its mac address(ARP)
Client sends data to server (UDP)

In any case Client will only receive ARP response. If server exists or not it will not get any UDP response? 

Client is using sendto function to send data. We can get error information after sendto call.

So my question is how this info is available when client doesn't get any response.
Error code can be get from WSAGetLastError.

I tried to send data to non existent host and sendto call succeeded . As per documentation it should fail with return value SOCKET_ERROR.

Any thoughts??

UDP Response

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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UDP不会发回任何ack，但它会发送任何响应吗？我已经设置了客户端服务器UDP程序。如果我给客户端发送数据到不存在的服务器，那么客户端会收到任何响应吗？我的假设是；客户端-->广播服务器地址(ARP)服务器-->使用其mac地址(ARP)回复客户端客户端将数据发送到服务器(UDP)在任何情况下，客户端都只能接收ARP响应。如果服务器存在或不存在，它将不会得到任何UDP响应？客户端正在使用sendt

问UDP响应
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回答 6

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