asio C++ library

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The BSD Socket API and Asio

The Asio library includes a low-level socket interface based on the BSD socket API, which is widely implemented and supported by extensive literature. It is also used as the basis for networking APIs in other languages, like Java. This low-level interface is designed to support the development of efficient and scalable applications. For example, it permits programmers to exert finer control over the number of system calls, avoid redundant data copying, minimise the use of resources like threads, and so on.

Unsafe and error prone aspects of the BSD socket API are not included. For example, the use of int to represent all sockets lacks type safety. The socket representation in Asio uses a distinct type for each protocol, e.g. for TCP one would use ip::tcp::socket, and for UDP one uses ip::udp::socket.

The following table shows the mapping between the BSD socket API and Asio:

BSD Socket API Elements

Equivalents in Asio

socket descriptor - int (POSIX) or SOCKET (Windows)

For TCP: ip::tcp::socket, ip::tcp::acceptor

For UDP: ip::udp::socket

basic_socket, basic_stream_socket, basic_datagram_socket, basic_raw_socket

in_addr, in6_addr

ip::address, ip::address_v4, ip::address_v6

sockaddr_in, sockaddr_in6

For TCP: ip::tcp::endpoint

For UDP: ip::udp::endpoint

ip::basic_endpoint

accept()

For TCP: ip::tcp::acceptor::accept()

basic_socket_acceptor::accept()

bind()

For TCP: ip::tcp::acceptor::bind(), ip::tcp::socket::bind()

For UDP: ip::udp::socket::bind()

basic_socket::bind()

close()

For TCP: ip::tcp::acceptor::close(), ip::tcp::socket::close()

For UDP: ip::udp::socket::close()

basic_socket::close()

connect()

For TCP: ip::tcp::socket::connect()

For UDP: ip::udp::socket::connect()

basic_socket::connect()

getaddrinfo(), gethostbyaddr(), gethostbyname(), getnameinfo(), getservbyname(), getservbyport()

For TCP: ip::tcp::resolver::resolve(), ip::tcp::resolver::async_resolve()

For UDP: ip::udp::resolver::resolve(), ip::udp::resolver::async_resolve()

ip::basic_resolver::resolve(), ip::basic_resolver::async_resolve()

gethostname()

ip::host_name()

getpeername()

For TCP: ip::tcp::socket::remote_endpoint()

For UDP: ip::udp::socket::remote_endpoint()

basic_socket::remote_endpoint()

getsockname()

For TCP: ip::tcp::acceptor::local_endpoint(), ip::tcp::socket::local_endpoint()

For UDP: ip::udp::socket::local_endpoint()

basic_socket::local_endpoint()

getsockopt()

For TCP: ip::tcp::acceptor::get_option(), ip::tcp::socket::get_option()

For UDP: ip::udp::socket::get_option()

basic_socket::get_option()

inet_addr(), inet_aton(), inet_pton()

ip::address::from_string(), ip::address_v4::from_string(), ip_address_v6::from_string()

inet_ntoa(), inet_ntop()

ip::address::to_string(), ip::address_v4::to_string(), ip_address_v6::to_string()

ioctl()

For TCP: ip::tcp::socket::io_control()

For UDP: ip::udp::socket::io_control()

basic_socket::io_control()

listen()

For TCP: ip::tcp::acceptor::listen()

basic_socket_acceptor::listen()

poll(), select(), pselect()

io_context::run(), io_context::run_one(), io_context::poll(), io_context::poll_one()

Note: in conjunction with asynchronous operations.

readv(), recv(), read()

For TCP: ip::tcp::socket::read_some(), ip::tcp::socket::async_read_some(), ip::tcp::socket::receive(), ip::tcp::socket::async_receive()

For UDP: ip::udp::socket::receive(), ip::udp::socket::async_receive()

basic_stream_socket::read_some(), basic_stream_socket::async_read_some(), basic_stream_socket::receive(), basic_stream_socket::async_receive(), basic_datagram_socket::receive(), basic_datagram_socket::async_receive()

recvfrom()

For UDP: ip::udp::socket::receive_from(), ip::udp::socket::async_receive_from()

basic_datagram_socket::receive_from(), basic_datagram_socket::async_receive_from()

send(), write(), writev()

For TCP: ip::tcp::socket::write_some(), ip::tcp::socket::async_write_some(), ip::tcp::socket::send(), ip::tcp::socket::async_send()

For UDP: ip::udp::socket::send(), ip::udp::socket::async_send()

basic_stream_socket::write_some(), basic_stream_socket::async_write_some(), basic_stream_socket::send(), basic_stream_socket::async_send(), basic_datagram_socket::send(), basic_datagram_socket::async_send()

sendto()

For UDP: ip::udp::socket::send_to(), ip::udp::socket::async_send_to()

basic_datagram_socket::send_to(), basic_datagram_socket::async_send_to()

setsockopt()

For TCP: ip::tcp::acceptor::set_option(), ip::tcp::socket::set_option()

For UDP: ip::udp::socket::set_option()

basic_socket::set_option()

shutdown()

For TCP: ip::tcp::socket::shutdown()

For UDP: ip::udp::socket::shutdown()

basic_socket::shutdown()

sockatmark()

For TCP: ip::tcp::socket::at_mark()

basic_socket::at_mark()

socket()

For TCP: ip::tcp::acceptor::open(), ip::tcp::socket::open()

For UDP: ip::udp::socket::open()

basic_socket::open()

socketpair()

local::connect_pair()

Note: POSIX operating systems only.


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