2023-10-24 21:59:30 -04:00
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< a name = "asio.overview.networking.protocols" > < / a > < a class = "link" href = "protocols.html" title = "TCP, UDP and ICMP" > TCP, UDP and ICMP< / a >
< / h4 > < / div > < / div > < / div >
< p >
Asio provides off-the-shelf support for the internet protocols TCP, UDP
and ICMP.
< / p >
< h6 >
< a name = "asio.overview.networking.protocols.h0" > < / a >
< span > < a name = "asio.overview.networking.protocols.tcp_clients" > < / a > < / span > < a class = "link" href = "protocols.html#asio.overview.networking.protocols.tcp_clients" > TCP
Clients< / a >
< / h6 >
< p >
Hostname resolution is performed using a resolver, where host and service
names are looked up and converted into one or more endpoints:
< / p >
< pre class = "programlisting" > < span class = "identifier" > ip< / span > < span class = "special" > ::< / span > < span class = "identifier" > tcp< / span > < span class = "special" > ::< / span > < span class = "identifier" > resolver< / span > < span class = "identifier" > resolver< / span > < span class = "special" > (< / span > < span class = "identifier" > my_io_context< / span > < span class = "special" > );< / span >
< span class = "identifier" > ip< / span > < span class = "special" > ::< / span > < span class = "identifier" > tcp< / span > < span class = "special" > ::< / span > < span class = "identifier" > resolver< / span > < span class = "special" > ::< / span > < span class = "identifier" > query< / span > < span class = "identifier" > query< / span > < span class = "special" > (< / span > < span class = "string" > "www.boost.org"< / span > < span class = "special" > ,< / span > < span class = "string" > "http"< / span > < span class = "special" > );< / span >
< span class = "identifier" > ip< / span > < span class = "special" > ::< / span > < span class = "identifier" > tcp< / span > < span class = "special" > ::< / span > < span class = "identifier" > resolver< / span > < span class = "special" > ::< / span > < span class = "identifier" > iterator< / span > < span class = "identifier" > iter< / span > < span class = "special" > =< / span > < span class = "identifier" > resolver< / span > < span class = "special" > .< / span > < span class = "identifier" > resolve< / span > < span class = "special" > (< / span > < span class = "identifier" > query< / span > < span class = "special" > );< / span >
< span class = "identifier" > ip< / span > < span class = "special" > ::< / span > < span class = "identifier" > tcp< / span > < span class = "special" > ::< / span > < span class = "identifier" > resolver< / span > < span class = "special" > ::< / span > < span class = "identifier" > iterator< / span > < span class = "identifier" > end< / span > < span class = "special" > ;< / span > < span class = "comment" > // End marker.< / span >
< span class = "keyword" > while< / span > < span class = "special" > (< / span > < span class = "identifier" > iter< / span > < span class = "special" > !=< / span > < span class = "identifier" > end< / span > < span class = "special" > )< / span >
< span class = "special" > {< / span >
< span class = "identifier" > ip< / span > < span class = "special" > ::< / span > < span class = "identifier" > tcp< / span > < span class = "special" > ::< / span > < span class = "identifier" > endpoint< / span > < span class = "identifier" > endpoint< / span > < span class = "special" > =< / span > < span class = "special" > *< / span > < span class = "identifier" > iter< / span > < span class = "special" > ++;< / span >
< span class = "identifier" > std< / span > < span class = "special" > ::< / span > < span class = "identifier" > cout< / span > < span class = "special" > < < < / span > < span class = "identifier" > endpoint< / span > < span class = "special" > < < < / span > < span class = "identifier" > std< / span > < span class = "special" > ::< / span > < span class = "identifier" > endl< / span > < span class = "special" > ;< / span >
< span class = "special" > }< / span >
< / pre >
< p >
The list of endpoints obtained above could contain both IPv4 and IPv6 endpoints,
so a program should try each of them until it finds one that works. This
keeps the client program independent of a specific IP version.
< / p >
< p >
To simplify the development of protocol-independent programs, TCP clients
may establish connections using the free functions < a class = "link" href = "../../reference/connect.html" title = "connect" > connect()< / a >
and < a class = "link" href = "../../reference/async_connect.html" title = "async_connect" > async_connect()< / a > .
These operations try each endpoint in a list until the socket is successfully
connected. For example, a single call:
< / p >
< pre class = "programlisting" > < span class = "identifier" > ip< / span > < span class = "special" > ::< / span > < span class = "identifier" > tcp< / span > < span class = "special" > ::< / span > < span class = "identifier" > socket< / span > < span class = "identifier" > socket< / span > < span class = "special" > (< / span > < span class = "identifier" > my_io_context< / span > < span class = "special" > );< / span >
< span class = "identifier" > asio< / span > < span class = "special" > ::< / span > < span class = "identifier" > connect< / span > < span class = "special" > (< / span > < span class = "identifier" > socket< / span > < span class = "special" > ,< / span > < span class = "identifier" > resolver< / span > < span class = "special" > .< / span > < span class = "identifier" > resolve< / span > < span class = "special" > (< / span > < span class = "identifier" > query< / span > < span class = "special" > ));< / span >
< / pre >
< p >
will synchronously try all endpoints until one is successfully connected.
Similarly, an asynchronous connect may be performed by writing:
< / p >
2023-10-25 13:08:15 -04:00
< pre class = "programlisting" > < span class = "identifier" > asio< / span > < span class = "special" > ::< / span > < span class = "identifier" > async_connect< / span > < span class = "special" > (< / span > < span class = "identifier" > local_socket< / span > < span class = "special" > ,< / span > < span class = "identifier" > iter< / span > < span class = "special" > ,< / span >
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< span class = "identifier" > boost< / span > < span class = "special" > ::< / span > < span class = "identifier" > bind< / span > < span class = "special" > (& < / span > < span class = "identifier" > client< / span > < span class = "special" > ::< / span > < span class = "identifier" > handle_connect< / span > < span class = "special" > ,< / span > < span class = "keyword" > this< / span > < span class = "special" > ,< / span >
< span class = "identifier" > asio< / span > < span class = "special" > ::< / span > < span class = "identifier" > placeholders< / span > < span class = "special" > ::< / span > < span class = "identifier" > error< / span > < span class = "special" > ));< / span >
< span class = "comment" > // ...< / span >
< span class = "keyword" > void< / span > < span class = "identifier" > handle_connect< / span > < span class = "special" > (< / span > < span class = "keyword" > const< / span > < span class = "identifier" > error_code< / span > < span class = "special" > & < / span > < span class = "identifier" > error< / span > < span class = "special" > )< / span >
< span class = "special" > {< / span >
< span class = "keyword" > if< / span > < span class = "special" > (!< / span > < span class = "identifier" > error< / span > < span class = "special" > )< / span >
< span class = "special" > {< / span >
< span class = "comment" > // Start read or write operations.< / span >
< span class = "special" > }< / span >
< span class = "keyword" > else< / span >
< span class = "special" > {< / span >
< span class = "comment" > // Handle error.< / span >
< span class = "special" > }< / span >
< span class = "special" > }< / span >
< / pre >
< p >
When a specific endpoint is available, a socket can be created and connected:
< / p >
< pre class = "programlisting" > < span class = "identifier" > ip< / span > < span class = "special" > ::< / span > < span class = "identifier" > tcp< / span > < span class = "special" > ::< / span > < span class = "identifier" > socket< / span > < span class = "identifier" > socket< / span > < span class = "special" > (< / span > < span class = "identifier" > my_io_context< / span > < span class = "special" > );< / span >
< span class = "identifier" > socket< / span > < span class = "special" > .< / span > < span class = "identifier" > connect< / span > < span class = "special" > (< / span > < span class = "identifier" > endpoint< / span > < span class = "special" > );< / span >
< / pre >
< p >
Data may be read from or written to a connected TCP socket using the < a class = "link" href = "../../reference/basic_stream_socket/receive.html" title = "basic_stream_socket::receive" > receive()< / a > ,
< a class = "link" href = "../../reference/basic_stream_socket/async_receive.html" title = "basic_stream_socket::async_receive" > async_receive()< / a > ,
< a class = "link" href = "../../reference/basic_stream_socket/send.html" title = "basic_stream_socket::send" > send()< / a > or
< a class = "link" href = "../../reference/basic_stream_socket/async_send.html" title = "basic_stream_socket::async_send" > async_send()< / a >
member functions. However, as these could result in < a class = "link" href = "../core/streams.html" title = "Streams, Short Reads and Short Writes" > short
writes or reads< / a > , an application will typically use the following
operations instead: < a class = "link" href = "../../reference/read.html" title = "read" > read()< / a > ,
< a class = "link" href = "../../reference/async_read.html" title = "async_read" > async_read()< / a > , < a class = "link" href = "../../reference/write.html" title = "write" > write()< / a >
and < a class = "link" href = "../../reference/async_write.html" title = "async_write" > async_write()< / a > .
< / p >
< h6 >
< a name = "asio.overview.networking.protocols.h1" > < / a >
< span > < a name = "asio.overview.networking.protocols.tcp_servers" > < / a > < / span > < a class = "link" href = "protocols.html#asio.overview.networking.protocols.tcp_servers" > TCP
Servers< / a >
< / h6 >
< p >
A program uses an acceptor to accept incoming TCP connections:
< / p >
< pre class = "programlisting" > < span class = "identifier" > ip< / span > < span class = "special" > ::< / span > < span class = "identifier" > tcp< / span > < span class = "special" > ::< / span > < span class = "identifier" > acceptor< / span > < span class = "identifier" > acceptor< / span > < span class = "special" > (< / span > < span class = "identifier" > my_io_context< / span > < span class = "special" > ,< / span > < span class = "identifier" > my_endpoint< / span > < span class = "special" > );< / span >
< span class = "special" > ...< / span >
< span class = "identifier" > ip< / span > < span class = "special" > ::< / span > < span class = "identifier" > tcp< / span > < span class = "special" > ::< / span > < span class = "identifier" > socket< / span > < span class = "identifier" > socket< / span > < span class = "special" > (< / span > < span class = "identifier" > my_io_context< / span > < span class = "special" > );< / span >
< span class = "identifier" > acceptor< / span > < span class = "special" > .< / span > < span class = "identifier" > accept< / span > < span class = "special" > (< / span > < span class = "identifier" > socket< / span > < span class = "special" > );< / span >
< / pre >
< p >
After a socket has been successfully accepted, it may be read from or written
to as illustrated for TCP clients above.
< / p >
< h6 >
< a name = "asio.overview.networking.protocols.h2" > < / a >
< span > < a name = "asio.overview.networking.protocols.udp" > < / a > < / span > < a class = "link" href = "protocols.html#asio.overview.networking.protocols.udp" > UDP< / a >
< / h6 >
< p >
UDP hostname resolution is also performed using a resolver:
< / p >
< pre class = "programlisting" > < span class = "identifier" > ip< / span > < span class = "special" > ::< / span > < span class = "identifier" > udp< / span > < span class = "special" > ::< / span > < span class = "identifier" > resolver< / span > < span class = "identifier" > resolver< / span > < span class = "special" > (< / span > < span class = "identifier" > my_io_context< / span > < span class = "special" > );< / span >
< span class = "identifier" > ip< / span > < span class = "special" > ::< / span > < span class = "identifier" > udp< / span > < span class = "special" > ::< / span > < span class = "identifier" > resolver< / span > < span class = "special" > ::< / span > < span class = "identifier" > query< / span > < span class = "identifier" > query< / span > < span class = "special" > (< / span > < span class = "string" > "localhost"< / span > < span class = "special" > ,< / span > < span class = "string" > "daytime"< / span > < span class = "special" > );< / span >
< span class = "identifier" > ip< / span > < span class = "special" > ::< / span > < span class = "identifier" > udp< / span > < span class = "special" > ::< / span > < span class = "identifier" > resolver< / span > < span class = "special" > ::< / span > < span class = "identifier" > iterator< / span > < span class = "identifier" > iter< / span > < span class = "special" > =< / span > < span class = "identifier" > resolver< / span > < span class = "special" > .< / span > < span class = "identifier" > resolve< / span > < span class = "special" > (< / span > < span class = "identifier" > query< / span > < span class = "special" > );< / span >
< span class = "special" > ...< / span >
< / pre >
< p >
A UDP socket is typically bound to a local endpoint. The following code
will create an IP version 4 UDP socket and bind it to the "any"
address on port < code class = "computeroutput" > < span class = "number" > 12345< / span > < / code > :
< / p >
< pre class = "programlisting" > < span class = "identifier" > ip< / span > < span class = "special" > ::< / span > < span class = "identifier" > udp< / span > < span class = "special" > ::< / span > < span class = "identifier" > endpoint< / span > < span class = "identifier" > endpoint< / span > < span class = "special" > (< / span > < span class = "identifier" > ip< / span > < span class = "special" > ::< / span > < span class = "identifier" > udp< / span > < span class = "special" > ::< / span > < span class = "identifier" > v4< / span > < span class = "special" > (),< / span > < span class = "number" > 12345< / span > < span class = "special" > );< / span >
< span class = "identifier" > ip< / span > < span class = "special" > ::< / span > < span class = "identifier" > udp< / span > < span class = "special" > ::< / span > < span class = "identifier" > socket< / span > < span class = "identifier" > socket< / span > < span class = "special" > (< / span > < span class = "identifier" > my_io_context< / span > < span class = "special" > ,< / span > < span class = "identifier" > endpoint< / span > < span class = "special" > );< / span >
< / pre >
< p >
Data may be read from or written to an unconnected UDP socket using the
< a class = "link" href = "../../reference/basic_datagram_socket/receive_from.html" title = "basic_datagram_socket::receive_from" > receive_from()< / a > ,
< a class = "link" href = "../../reference/basic_datagram_socket/async_receive_from.html" title = "basic_datagram_socket::async_receive_from" > async_receive_from()< / a > ,
< a class = "link" href = "../../reference/basic_datagram_socket/send_to.html" title = "basic_datagram_socket::send_to" > send_to()< / a >
or < a class = "link" href = "../../reference/basic_datagram_socket/async_send_to.html" title = "basic_datagram_socket::async_send_to" > async_send_to()< / a >
member functions. For a connected UDP socket, use the < a class = "link" href = "../../reference/basic_datagram_socket/receive.html" title = "basic_datagram_socket::receive" > receive()< / a > ,
< a class = "link" href = "../../reference/basic_datagram_socket/async_receive.html" title = "basic_datagram_socket::async_receive" > async_receive()< / a > ,
< a class = "link" href = "../../reference/basic_datagram_socket/send.html" title = "basic_datagram_socket::send" > send()< / a >
or < a class = "link" href = "../../reference/basic_datagram_socket/async_send.html" title = "basic_datagram_socket::async_send" > async_send()< / a >
member functions.
< / p >
< h6 >
< a name = "asio.overview.networking.protocols.h3" > < / a >
< span > < a name = "asio.overview.networking.protocols.icmp" > < / a > < / span > < a class = "link" href = "protocols.html#asio.overview.networking.protocols.icmp" > ICMP< / a >
< / h6 >
< p >
As with TCP and UDP, ICMP hostname resolution is performed using a resolver:
< / p >
< pre class = "programlisting" > < span class = "identifier" > ip< / span > < span class = "special" > ::< / span > < span class = "identifier" > icmp< / span > < span class = "special" > ::< / span > < span class = "identifier" > resolver< / span > < span class = "identifier" > resolver< / span > < span class = "special" > (< / span > < span class = "identifier" > my_io_context< / span > < span class = "special" > );< / span >
< span class = "identifier" > ip< / span > < span class = "special" > ::< / span > < span class = "identifier" > icmp< / span > < span class = "special" > ::< / span > < span class = "identifier" > resolver< / span > < span class = "special" > ::< / span > < span class = "identifier" > query< / span > < span class = "identifier" > query< / span > < span class = "special" > (< / span > < span class = "string" > "localhost"< / span > < span class = "special" > ,< / span > < span class = "string" > ""< / span > < span class = "special" > );< / span >
< span class = "identifier" > ip< / span > < span class = "special" > ::< / span > < span class = "identifier" > icmp< / span > < span class = "special" > ::< / span > < span class = "identifier" > resolver< / span > < span class = "special" > ::< / span > < span class = "identifier" > iterator< / span > < span class = "identifier" > iter< / span > < span class = "special" > =< / span > < span class = "identifier" > resolver< / span > < span class = "special" > .< / span > < span class = "identifier" > resolve< / span > < span class = "special" > (< / span > < span class = "identifier" > query< / span > < span class = "special" > );< / span >
< span class = "special" > ...< / span >
< / pre >
< p >
An ICMP socket may be bound to a local endpoint. The following code will
create an IP version 6 ICMP socket and bind it to the "any" address:
< / p >
< pre class = "programlisting" > < span class = "identifier" > ip< / span > < span class = "special" > ::< / span > < span class = "identifier" > icmp< / span > < span class = "special" > ::< / span > < span class = "identifier" > endpoint< / span > < span class = "identifier" > endpoint< / span > < span class = "special" > (< / span > < span class = "identifier" > ip< / span > < span class = "special" > ::< / span > < span class = "identifier" > icmp< / span > < span class = "special" > ::< / span > < span class = "identifier" > v6< / span > < span class = "special" > (),< / span > < span class = "number" > 0< / span > < span class = "special" > );< / span >
< span class = "identifier" > ip< / span > < span class = "special" > ::< / span > < span class = "identifier" > icmp< / span > < span class = "special" > ::< / span > < span class = "identifier" > socket< / span > < span class = "identifier" > socket< / span > < span class = "special" > (< / span > < span class = "identifier" > my_io_context< / span > < span class = "special" > ,< / span > < span class = "identifier" > endpoint< / span > < span class = "special" > );< / span >
< / pre >
< p >
The port number is not used for ICMP.
< / p >
< p >
Data may be read from or written to an unconnected ICMP socket using the
< a class = "link" href = "../../reference/basic_raw_socket/receive_from.html" title = "basic_raw_socket::receive_from" > receive_from()< / a > ,
< a class = "link" href = "../../reference/basic_raw_socket/async_receive_from.html" title = "basic_raw_socket::async_receive_from" > async_receive_from()< / a > ,
< a class = "link" href = "../../reference/basic_raw_socket/send_to.html" title = "basic_raw_socket::send_to" > send_to()< / a >
or < a class = "link" href = "../../reference/basic_raw_socket/async_send_to.html" title = "basic_raw_socket::async_send_to" > async_send_to()< / a >
member functions.
< / p >
< h6 >
< a name = "asio.overview.networking.protocols.h4" > < / a >
< span > < a name = "asio.overview.networking.protocols.see_also" > < / a > < / span > < a class = "link" href = "protocols.html#asio.overview.networking.protocols.see_also" > See
Also< / a >
< / h6 >
< p >
< a class = "link" href = "../../reference/ip__tcp.html" title = "ip::tcp" > ip::tcp< / a > , < a class = "link" href = "../../reference/ip__udp.html" title = "ip::udp" > ip::udp< / a > ,
< a class = "link" href = "../../reference/ip__icmp.html" title = "ip::icmp" > ip::icmp< / a > , < a class = "link" href = "../../tutorial/tutdaytime1.html" title = "Daytime.1 - A synchronous TCP daytime client" > daytime
protocol tutorials< / a > , < a class = "link" href = "../../examples/cpp03_examples.html#asio.examples.cpp03_examples.icmp" > ICMP
ping example< / a > .
< / p >
< / div >
< div class = "copyright-footer" > Copyright © 2003-2023 Christopher M. Kohlhoff< p >
Distributed under the Boost Software License, Version 1.0. (See accompanying
file LICENSE_1_0.txt or copy at < a href = "http://www.boost.org/LICENSE_1_0.txt" target = "_top" > http://www.boost.org/LICENSE_1_0.txt< / a > )
< / p >
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< a accesskey = "p" href = "../networking.html" > < img src = "../../../prev.png" alt = "Prev" > < / a > < a accesskey = "u" href = "../networking.html" > < img src = "../../../up.png" alt = "Up" > < / a > < a accesskey = "h" href = "../../../index.html" > < img src = "../../../home.png" alt = "Home" > < / a > < a accesskey = "n" href = "other_protocols.html" > < img src = "../../../next.png" alt = "Next" > < / a >
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