blocks|key|1507501|text|getpeername给出了客户端的详细信息，而不是服务器的详细信息，所以你可以得到一些随机的端口。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1507502|您可以看到man页面|offset|length|1507503|干杯|1507504|entityMap|0|LINK|mutability|MUTABLE|url|http://www.manpagez.com/man/2/getpeername/^0|0|5|3|0|0|0^^$0|@$1|2|3|4|5|6|7|P|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|Q|8|@]|9|@$D|R|E|S|1|T]]|A|$]]|$1|F|3|G|5|6|7|U|8|@]|9|@]|A|$]]|$1|H|3|-4|5|6|7|V|8|@]|9|@]|A|$]]]|I|$J|$5|K|L|M|A|$N|O]]]]

getpeername give details about the client not the server so it make sense you get some random port. 

you can see the <a href="http://www.manpagez.com/man/2/getpeername/" rel="nofollow noreferrer">man</a> page

Cheers

blocks|key|1507540|text|为了详细说明RageZ的答案，getpeername()返回源端口和套接字另一端的地址。端口12345是您传递给bind()的目标地址。一般而言，客户端(例如telnet、nc等)不会在套接字上调用bind()，因为它们不想侦听连接。因此，操作系统将为它们分配一个任意的“临时”端口号。|type|unstyled|depth|inlineStyleRanges|offset|length|style|BOLD|entityRanges|data|1507541|通常，在知道TCP连接的源端口方面几乎没有什么用处。|1507542|entityMap^0|U|1|0|0^^$0|@$1|2|3|4|5|6|7|J|8|@$9|K|A|L|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|M|8|@]|D|@]|E|$]]|$1|H|3|-4|5|6|7|N|8|@]|D|@]|E|$]]]|I|$]]

To elaborate on RageZ's answer, getpeername() is returning the source port and address of the other side of your socket. Port 12345 is the address of the destination that you passed to bind(). In general, clients (e.g. telnet, nc, etc...) will not have called bind() on their socket because they don't want to listen for connections. So the OS will assign them an arbitrary "ephemeral" port number.

In general, there is little to no utility in knowing the source port of a TCP connection.

blocks|key|102200|text|如果%25s已连接，则应获取127.0.0.1:12345。你确定它是连接的吗？|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|102201|您需要检查getpeername()的返回码，以确保没有错误。|102202|entityMap^0|C|F|0|5|D|0^^$0|@$1|2|3|4|5|6|7|J|8|@$9|K|A|L|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|M|8|@$9|N|A|O|B|C]]|D|@]|E|$]]|$1|H|3|-4|5|6|7|P|8|@]|D|@]|E|$]]]|I|$]]

You should get <code>127.0.0.1:12345</code> if s is connected. Are you sure it's connected?

You need to check return code of <code>getpeername()</code> to make sure there is no errors.

blocks|key|1507598|text|看起来你有两个进程在监听两个端口--也就是两个相互独立的监听套接字。然后，在其中一个进程中创建第三个客户端套接字，并连接到另一个进程。第三个套接字通过TCP+stack+(在您的示例中是62305)分配给它一个ephemeral+port。因此连接由元组{源ip，源端口，目标ip，目标端口}-+{127.0.0.1,62305,127.0.0.1,54321}表示。此连接与连接进程可能具有的任何侦听套接字完全无关。如果您需要知道端口号，您必须显式地设计您的应用程序以在对等方之间通信端口号。如果你只想知道哪个进程有什么套接字，总会有lsof。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1507599|entityMap|0|LINK|mutability|MUTABLE|url|http://en.wikipedia.org/wiki/Ephemeral_port|1|http://en.wikipedia.org/wiki/Lsof^0|2X|E|0|7G|4|1|0^^$0|@$1|2|3|4|5|6|7|N|8|@]|9|@$A|O|B|P|1|Q]|$A|R|B|S|1|T]]|C|$]]|$1|D|3|-4|5|6|7|U|8|@]|9|@]|C|$]]]|E|$F|$5|G|H|I|C|$J|K]]|L|$5|G|H|I|C|$J|M]]]]

It looks like you have two processes listening on two ports - that's two listening sockets independent of each other. Then you create a third, client, socket in one of the processes and connect to the other one. That third socket gets an <a href="http://en.wikipedia.org/wiki/Ephemeral_port" rel="nofollow noreferrer">ephemeral port</a> assigned to it by TCP stack (62305 in your case). So the connection is represented by the tuple {source ip, source port, target ip, target port} - {127.0.0.1,62305,127.0.0.1,54321} here. This connection has absolutely nothing to do with any listening sockets the connecting process might have. You have to explicitly design your application to communicate port numbers among peers if you need to know them. If you just want to know what process has what sockets, there's always <a href="http://en.wikipedia.org/wiki/Lsof" rel="nofollow noreferrer">lsof</a>.

EDIT: Restating the problem, if I am listening to port 54321 and a local process listening to port 12345 connects to me, creating socket <code>s</code>, how do I actually find the port it is listening on?

<pre><code>sockaddr_in addr;
int len = sizeof(addr);
getpeername(s, (sockaddr*)&amp;addr, &amp;len);
cout &lt;&lt; string(inet_ntoa(addr.sin_addr)) &lt;&lt; ":" &lt;&lt; ntohs(addr.sin_port) &lt;&lt; endl;
</code></pre>

Shouldn't the output be <code>127.0.0.1:12345</code>? Instead I get <code>127.0.0.1:62305</code>, or some other arbitrary port number. Is this an error on my part, or is it supposed to be this way?

getpeername() doesn't work with connections to localhost

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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编辑:重复这个问题，如果我正在侦听端口54321，并且侦听端口12345的本地进程连接到我，创建套接字s，我如何找到它正在侦听的端口？sockaddr_in addr;int len = sizeof(addr);getpeername(s, (sockaddr*)&addr, &len);cout << string...

问getpeername()不适用于与本地主机的连接
EN

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问getpeername()不适用于与本地主机的连接EN