Implement dial, support IPv6 in httpclient (#5763)

* Implement dial, support IPv6 in httpclient

Added ``dial`` procedure to networking modules: ``net``, ``asyncdispatch``,
``asyncnet``. It merges socket creation, address resolution, and connection
into single step. When using ``dial``, you don't have to worry about
IPv4 vs IPv6 problem.

Fixed addrInfo loop in connect to behave properly.
Previously it would stop on first non-immediate failure, instead of
continuing and trying the remaining addresses.

Fixed newAsyncNativeSocket to raise proper error if socket creation
fails.

Fixes: #3811

* Check domain during connect() only on non-Windows

This is how it was in the previous implementation of connect().

* Call 'osLastError' before 'close' in net.dial

* Record osLastError before freeAddrInfo in net.dial

* Add missing docs for 'dial' proc

* Optimize dial to create one FD per domain, add tests

And make async IPv6 servers work on Windows.

* Add IPv6 test to uri module

* Fix getAddrString error handling

1 files changed, 60 insertions, 0 deletions

diff --git a/tests/stdlib/tnetdial.nim b/tests/stdlib/tnetdial.nim
new file mode 100644
index 000000000..da6088d70
--- /dev/null
+++ b/tests/stdlib/tnetdial.nim
@@ -0,0 +1,60 @@
+discard """
+  cmd: "nim c --threads:on $file"
+  exitcode: 0
+  output: "OK"
+"""
+
+import os, net, nativesockets, asyncdispatch
+
+## Test for net.dial
+
+const port = Port(28431)
+
+proc initIPv6Server(hostname: string, port: Port): AsyncFD =
+  let fd = newNativeSocket(AF_INET6)
+  setSockOptInt(fd, SOL_SOCKET, SO_REUSEADDR, 1)
+  var aiList = getAddrInfo(hostname, port, AF_INET6)
+  if bindAddr(fd, aiList.ai_addr, aiList.ai_addrlen.Socklen) < 0'i32:
+    freeAddrInfo(aiList)
+    raiseOSError(osLastError())
+  freeAddrInfo(aiList)
+  if listen(fd) != 0:
+    raiseOSError(osLastError())
+  setBlocking(fd, false)
+
+  var serverFd = fd.AsyncFD
+  register(serverFd)
+  result = serverFd
+
+# Since net.dial is synchronous, we use main thread to setup server,
+# and dial to it from another thread.
+
+proc testThread() {.thread.} =
+  let fd = net.dial("::1", port)
+  var s = newString(5)
+  doAssert fd.recv(addr s[0], 5) == 5
+  if s == "Hello":
+    echo "OK"
+  fd.close()
+
+proc test() =
+  var t: Thread[void]
+  createThread(t, testThread)
+
+  let serverFd = initIPv6Server("::1", port)
+  var done = false
+
+  serverFd.accept().callback = proc(fut: Future[AsyncFD]) =
+    serverFd.closeSocket()
+    if not fut.failed:
+      let fd = fut.read()
+      fd.send("Hello").callback = proc() =
+        fd.closeSocket()
+        done = true
+
+  while not done:
+    poll()
+
+  joinThread(t)
+
+test()