Add support for Unix sockets to HTTP::Server

spec/std/http/server/server_spec.cr

@@ -40,6 +40,23 @@ private class ReverseResponseOutput < IO
   end
 end
 
+# TODO: replace with `HTTP::Client` once it supports connecting to Unix socket.
+private def unix_request(path)
+  UNIXSocket.open(path) do |io|
+    io << "GET / HTTP/1.1"
+    io << "\r\n\r\n"
+    io.flush
+
+    loop do
+      line = io.gets || break
+
+      if line.empty?
+        return io.gets
+      end
+    end
+  end
+end
+
 module HTTP
   class Server
     describe Response do
@@ -263,6 +280,44 @@ module HTTP
       HTTP::Client.get("http://127.0.0.1:#{port1}/").body.should eq "Test Server (127.0.0.1:#{port1})"
       HTTP::Client.get("http://127.0.0.1:#{port1}/").body.should eq "Test Server (127.0.0.1:#{port1})"
     end
+
+    {% if flag?(:unix) %}
+    it "binds to different unix sockets" do
+      path1 = "/tmp/socket1"
+      path2 = "/tmp/socket2"
+
+      begin
+        server = Server.new do |context|
+          socket = context.socket
+
+          socket.should be_a(UNIXSocket)
+          if socket.is_a? UNIXSocket
+            context.response.puts "Test Server (#{socket.local_address})"
+          end
+        end
+
+        socket1 = server.bind UNIXServer.new(path1)
+        socket2 = server.bind "unix:#{path2}"
+
+        spawn do
+          server.listen
+        end
+
+        Fiber.yield
+
+        unix_request(path1).should eq "Test Server (#{path1})"
+        unix_request(path2).should eq "Test Server (#{path2})"
+
+        server.close
+
+        File.exists?(path1).should be_false
+        File.exists?(path2).should be_false
+      ensure
+        File.delete(path1) if File.exists?(path1)
+        File.delete(path2) if File.exists?(path2)
+      end
+    end
+    {% end %}
   end
 
   describe HTTP::Server::RequestProcessor do

src/http/server.cr

@@ -156,7 +156,44 @@ class HTTP::Server
     tcp_server.local_address.port
   end
 
-  # Creates a `TCPServer` bound to *address* and adds it as a socket.
+  # Creates a `Socket::Server` listenting to *address* and adds it as a socket.
+  #
+  # The *address* can either be `host:port` or a Unix socket prefixed by `unix:`.
+  # This works only on systems supporting Unix sockets.
+  #
+  # ```
+  # server = HTTP::Server.new { }
+  # server.bind "127.0.0.1:8080"
+  # server.bind "unix:/tmp/my-socket"
+  # ```
+  def bind(address : String, reuse_port : Bool = false) : Socket::Server
+    if address.starts_with?("unix:")
+      bind(Socket::UNIXAddress.new(address[5..-1])).as(Socket::Server)
+    else
+      host, _, port = address.partition(':')
+      if host == "*" || host.empty?
+        host = "0.0.0.0"
+      end
+      if port.empty?
+        port = 80
+      else
+        port = port.to_i
+      end
+      bind(host, port, reuse_port).as(Socket::Server)
+    end
+  end
+
+  # Creates a `UNIXServer` bound to *address* and adds it as an interface.
+  #
+  # ```
+  # server = HTTP::Server.new { }
+  # server.bind Socket::UNIXAddress.new("/tmp/my-socket")
+  # ```
+  def bind(address : Socket::UNIXAddress) : UNIXServer
+    bind UNIXServer.new(address.path)
+  end
+
+  # Creates a `TCPServer` bound to *address* and adds it as an interface.
   #
   # ```
   # server = HTTP::Server.new { }