Re: [Boost-users] [asio] Howto bind *client* to a specific port?

Subject: Re: [Boost-users] [asio] Howto bind *client* to a specific port?
From: OvermindDL1 (overminddl1_at_[hidden])
Date: 2010-10-02 18:45:21

On Sat, Oct 2, 2010 at 6:15 AM, for-gmane <for-gmane_at_[hidden]> wrote:
> On 2010-10-01 22:51, for-gmane wrote:
>>
>> On 2010-10-01 17:03, for-gmane wrote:
>>>
>>> A NewbieQ:
>>>
>>> From a client app I want to connect to a server app on a remote host
>>> (say port 6666).
>>> A requirement is that the client shall be bound to a defined port (say
>>> port 5555).
>>> How to do this in asio?
>>> Does the client need to use an acceptor? (ok, this maybe sounds
>>> non-sensical, but who knows... :-)
>>
>> Solved as follows:
>> ...
>> tcp::socket s(io_service);
>> s.open(tcp::v4());
>> s.set_option(tcp::socket::reuse_address(true));
>> s.bind(tcp::endpoint(tcp::v4(), uLocalPortToUse));
>> s.connect(*iterator);
>> ...
>
> Just a followup question:
>
> I tried to replace the above s.bind(...) with this one:
> Â s.bind(tcp::endpoint(boost::asio::ip::address::from_string("127.0.0.1"),
> uLocalPortToUse));
> but then, the s.connect(...) call to internet hosts fails.
> Is this behaviour correct? Â (Ie. connecting from 127.0.0.1 seems not
> possible to non-local adresses; OTOH this make sense, isn't it?)

Correct, 127.0.0.1 is not on the network, it is the local loopback
connection (the entire 127/8 range is I think), hence you can only
connect to something on it from the local loopback connection (like
127.0.0.2 or whatnot).  If you want it externally visible, you must
put it on a connection that your network card manages (maybe
192.168.1.1 or so?  Whatever you are).