Remove HTTP::Server#port and add HTTP::Server#bind_unused_port

The return type is now an Socket::IPAddress instead of only the port number.

spec/std/http/server/server_spec.cr

@@ -194,22 +194,19 @@ module HTTP
   end
 
   describe HTTP::Server do
-    it "re-sets special port zero after bind" do
+    it "binds to unused port" do
       server = Server.new { |ctx| }
-      server.bind 0
-      server.port.should_not eq(0)
-    end
+      address = server.bind_unused_port
+      address.port.should_not eq(0)
 
-    it "re-sets port to nil after close" do
       server = Server.new { |ctx| }
-      server.bind 0
-      server.close
-      server.port.should be_nil
+      port = server.bind(0).port
+      port.should_not eq(0)
     end
 
     it "doesn't raise on accept after close #2692" do
       server = Server.new { }
-      server.bind "0.0.0.0", 0
+      server.bind_unused_port
 
       spawn do
         server.close
@@ -221,34 +218,35 @@ module HTTP
 
     it "reuses the TCP port (SO_REUSEPORT)" do
       s1 = Server.new { |ctx| }
-      s1.bind(0, reuse_port: true)
+      address = s1.bind_unused_port(reuse_port: true)
 
       s2 = Server.new { |ctx| }
-      s2.bind(s1.port.not_nil!, reuse_port: true)
+      s2.bind(address.port, reuse_port: true)
 
       s1.close
       s2.close
     end
 
-    it "binds to different interfaces" do
+    it "binds to different ports" do
       server = Server.new do |context|
         context.response.print "Test Server (#{context.request.headers["Host"]?})"
       end
 
-      address1 = server.bind(0)
-      address2 = server.bind(0)
+      tcp_server = TCPServer.new("127.0.0.1", 0)
+      server.bind tcp_server
+      address1 = tcp_server.local_address
+
+      address2 = server.bind_unused_port
 
-      port1 = address1.port
-      port2 = address2.port
-      port1.should_not eq port2
+      address1.should_not eq address2
 
       spawn { server.listen }
 
       Fiber.yield
 
-      HTTP::Client.get("http://127.0.0.1:#{port2}/").body.should eq "Test Server (127.0.0.1:#{port2})"
-      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})"
+      HTTP::Client.get("http://#{address2}/").body.should eq "Test Server (#{address2})"
+      HTTP::Client.get("http://#{address1}/").body.should eq "Test Server (#{address1})"
+      HTTP::Client.get("http://#{address1}/").body.should eq "Test Server (#{address1})"
     end
   end
 

spec/std/http/web_socket_spec.cr

@@ -295,7 +295,7 @@ describe HTTP::WebSocket do
   end
 
   it "negotiates over HTTP correctly" do
-    port_chan = Channel(Int32).new
+    address_chan = Channel(Socket::IPAddress).new
 
     spawn do
       http_ref = nil
@@ -314,14 +314,14 @@ describe HTTP::WebSocket do
       end
 
       http_server = http_ref = HTTP::Server.new([ws_handler])
-      http_server.bind 0
-      port_chan.send(http_server.port.not_nil!)
+      address = http_server.bind_unused_port
+      address_chan.send(address)
       http_server.listen
     end
 
-    listen_port = port_chan.receive
+    listen_address = address_chan.receive
 
-    ws2 = HTTP::WebSocket.new("ws://127.0.0.1:#{listen_port}/foo/bar?query=arg&yes=please")
+    ws2 = HTTP::WebSocket.new("ws://#{listen_address}/foo/bar?query=arg&yes=please")
 
     random = Random::Secure.hex
     ws2.on_message do |str|
@@ -334,7 +334,7 @@ describe HTTP::WebSocket do
   end
 
   it "negotiates over HTTPS correctly" do
-    port_chan = Channel(Int32).new
+    address_chan = Channel(Socket::IPAddress).new
 
     spawn do
       http_ref = nil
@@ -354,15 +354,15 @@ describe HTTP::WebSocket do
       tls = http_server.tls = OpenSSL::SSL::Context::Server.new
       tls.certificate_chain = File.join(__DIR__, "../openssl/ssl/openssl.crt")
       tls.private_key = File.join(__DIR__, "../openssl/ssl/openssl.key")
-      http_server.bind 0
-      port_chan.send(http_server.port.not_nil!)
+      address = http_server.bind_unused_port
+      address_chan.send(address)
       http_server.listen
     end
 
-    listen_port = port_chan.receive
+    listen_address = address_chan.receive
 
     client_context = OpenSSL::SSL::Context::Client.insecure
-    ws2 = HTTP::WebSocket.new("127.0.0.1", port: listen_port, path: "/", tls: client_context)
+    ws2 = HTTP::WebSocket.new(listen_address.address, port: listen_address.port, path: "/", tls: client_context)
 
     random = Random::Secure.hex
     ws2.on_message do |str|

src/http/server.cr

@@ -163,6 +163,18 @@ class HTTP::Server
     bind "127.0.0.1", port, reuse_port
   end
 
+  # Creates a `TCPServer` listening on an unused port and adds it as a socket.
+  #
+  # Returns the `Socket::IPAddress` with the determined port number.
+  #
+  # ```
+  # server = HTTP::Server.new { }
+  # server.bind_unused_port # => Socket::IPAddress.new("127.0.0.1", 12345)
+  # ```
+  def bind_unused_port(host : String = "127.0.0.1", reuse_port : Bool = false) : Socket::IPAddress
+    bind host, 0, reuse_port
+  end
+
   # Adds a `Socket::Server` *socket* to this server.
   def bind(socket : Socket::Server) : Socket::Server
     @sockets << socket