diff --git a/lib/httpx/channel.rb b/lib/httpx/channel.rb
index 9bab7fc9..60588430 100644
--- a/lib/httpx/channel.rb
+++ b/lib/httpx/channel.rb
@@ -77,11 +77,26 @@ module HTTPX
       @write_buffer = Buffer.new(BUFFER_SIZE)
       @pending = []
       on(:error) { |ex| on_error(ex) }
-      transition(:idle)
+      if @options.io
+        # if there's an already open IO, get its
+        # peer address, and force-initiate the parser
+        transition(:already_open)
+        @io = IO.registry(@type).new(@uri, nil, @options)
+        parser
+      else
+        transition(:idle)
+      end
     end
 
+    # this is a semi-private method, to be used by the resolver
+    # to initiate the io object.
     def addresses=(addrs)
-      @io = IO.registry(@type).new(@uri, addrs, @options)
+      @io ||= IO.registry(@type).new(@uri, addrs, @options) # rubocop:disable Naming/MemoizedInstanceVariableName
+    end
+
+    def addresses
+      return unless @io
+      @io.addresses
     end
 
     def mergeable?(addresses)
@@ -342,6 +357,11 @@ module HTTPX
 
         @io.close
         @read_buffer.clear
+      when :already_open
+        nextstate = :open
+        send_pending
+        @timeout_threshold = @options.timeout.operation_timeout
+        @timeout = @timeout_threshold
       end
       @state = nextstate
     rescue Errno::EHOSTUNREACH
diff --git a/lib/httpx/connection.rb b/lib/httpx/connection.rb
index f6898e79..79ee2526 100644
--- a/lib/httpx/connection.rb
+++ b/lib/httpx/connection.rb
@@ -120,12 +120,20 @@ module HTTPX
     end
 
     def register_channel(channel)
-      @timeout.transition(:idle)
-      monitor = @selector.register(channel, :w)
+      monitor = if channel.state == :open
+        # if open, an IO was passed upstream, therefore
+        # consider it connected already.
+        @connected_channels += 1
+        @selector.register(channel, :rw)
+      else
+        @selector.register(channel, :w)
+      end
       monitor.value = channel
       channel.on(:close) do
         unregister_channel(channel)
       end
+      return if channel.state == :open
+      @timeout.transition(:idle)
     end
 
     def unregister_channel(channel)
diff --git a/lib/httpx/io/tcp.rb b/lib/httpx/io/tcp.rb
index ce47f7ba..b2bde623 100644
--- a/lib/httpx/io/tcp.rb
+++ b/lib/httpx/io/tcp.rb
@@ -17,24 +17,25 @@ module HTTPX
       @state = :idle
       @hostname = uri.host
       @addresses = addresses
-      @ip_index = @addresses.size - 1
       @options = Options.new(options)
       @fallback_protocol = @options.fallback_protocol
       @port = uri.port
       if @options.io
         @io = case @options.io
               when Hash
-                @ip = @addresses[@ip_index]
-                @options.io[@ip] || @options.io["#{@ip}:#{@port}"]
+                @options.io[uri.authority]
               else
-                @ip = @hostname
                 @options.io
         end
+        _, _, _, @ip = @io.addr
+        @addresses ||= [@ip]
+        @ip_index = @addresses.size - 1
         unless @io.nil?
           @keep_open = true
           @state = :connected
         end
       else
+        @ip_index = @addresses.size - 1
         @ip = @addresses[@ip_index]
       end
       @io ||= build_socket
diff --git a/lib/httpx/resolver/resolver_mixin.rb b/lib/httpx/resolver/resolver_mixin.rb
index f8a7e744..edd1bb39 100644
--- a/lib/httpx/resolver/resolver_mixin.rb
+++ b/lib/httpx/resolver/resolver_mixin.rb
@@ -36,7 +36,10 @@ module HTTPX
       end
 
       def early_resolve(channel, hostname: channel.uri.host)
-        addresses = ip_resolve(hostname) || Resolver.cached_lookup(hostname) || system_resolve(hostname)
+        addresses = channel.addresses ||
+                    ip_resolve(hostname) ||
+                    Resolver.cached_lookup(hostname) ||
+                    system_resolve(hostname)
         return unless addresses
 
         emit_addresses(channel, addresses)