How is Ruby TCPSocket timeout defined?
ruby, sockets
Solution
Use `begin .. rescue Errno::ETIMEDOUT` to catch the timeout:
require 'socket'
begin
TCPSocket.new('www.example.com', 111)
rescue Errno::ETIMEDOUT
p 'timeout'
end
To catch any socket exceptions, use `SystemCallError` instead.
According to the SystemCallError documentation:
SystemCallError is the base class for all low-level platform-dependent errors.
The errors available on the current platform are subclasses of SystemCallError and are defined in the Errno module.
`TCPSocket.new` does not support timeout directly.
Use `Socket::connect_non_blocking` and `IO::select` to set timeout.
require 'socket'
def connect(host, port, timeout = 5)
# Convert the passed host into structures the non-blocking calls
# can deal with
addr = Socket.getaddrinfo(host, nil)
sockaddr = Socket.pack_sockaddr_in(port, addr[0][4])
Socket.new(Socket.const_get(addr[0][0]), Socket::SOCK_STREAM, 0).tap do |socket|
socket.setsockopt(Socket::IPPROTO_TCP, Socket::TCP_NODELAY, 1)
begin
# Initiate the socket connection in the background. If it doesn't fail
# immediatelyit will raise an IO::WaitWritable (Errno::EINPROGRESS)
# indicating the connection is in progress.
socket.connect_nonblock(sockaddr)
rescue IO::WaitWritable
# IO.select will block until the socket is writable or the timeout
# is exceeded - whichever comes first.
if IO.select(nil, [socket], nil, timeout)
begin
# Verify there is now a good connection
socket.connect_nonblock(sockaddr)
rescue Errno::EISCONN
# Good news everybody, the socket is connected!
rescue
# An unexpected exception was raised - the connection is no good.
socket.close
raise
end
else
# IO.select returns nil when the socket is not ready before timeout
# seconds have elapsed
socket.close
raise "Connection timeout"
end
end
end
end
connect('www.example.com', 111, 2)
The above code comes from "Setting a Socket Connection Timeout in Ruby".
Problem
``` $ irb 1.9.3-p448 :001 > require 'socket' => true 1.9.3-p448 :002 > TCPSocket.new('www.example.com', 111) ``` gives Errno::ETIMEDOUT: Operation timed out - connect(2) Questions: - How can I define the timeout value for `TCPSocket.new`? - How can I properly catch the timeout (or, in general, socket) exception(s)?