Update networking layer w/ CURL and emscripten impl

External/curl-8.17.0/tests/data/test504

@@ -0,0 +1,43 @@
+<testcase>
+<info>
+<keywords>
+HTTP
+HTTP GET
+HTTP proxy
+multi
+FAILURE
+connect to non-listen
+</keywords>
+</info>
+
+# Server-side
+<reply>
+</reply>
+
+# Client-side
+<client>
+<features>
+http
+proxy
+</features>
+# tool is what to use instead of 'curl'
+<tool>
+lib%TESTNUMBER
+</tool>
+
+<name>
+simple multi through local proxy without listener
+</name>
+<command>
+http://%HOSTIP:%NOLISTENPORT/%TESTNUMBER %HOSTIP:%NOLISTENPORT
+</command>
+</client>
+
+# Verify data after the test has been "shot"
+# TEST_ERR_SUCCESS is errorcode 41
+<verify>
+<errorcode>
+41
+</errorcode>
+</verify>
+</testcase>