Index: lldb/test/API/tools/lldb-server/TestPtyServer.py
===================================================================
--- /dev/null
+++ lldb/test/API/tools/lldb-server/TestPtyServer.py
@@ -0,0 +1,73 @@
+import gdbremote_testcase
+import lldbgdbserverutils
+from lldbsuite.test.decorators import *
+from lldbsuite.test.lldbtest import *
+from lldbgdbserverutils import *
+
+import xml.etree.ElementTree as ET
+
+
+@skipIfWindows
+class PtyServerTestCase(gdbremote_testcase.GdbRemoteTestCaseBase):
+    mydir = TestBase.compute_mydir(__file__)
+
+    def setUp(self):
+        super().setUp()
+        import pty
+        import tty
+        master, slave = pty.openpty()
+        tty.setraw(master)
+        self._master = io.FileIO(master, 'r+b')
+        self._slave = io.FileIO(slave, 'r+b')
+
+    def get_debug_monitor_command_line_args(self, attach_pid=None):
+        commandline_args = self.debug_monitor_extra_args
+        if attach_pid:
+            commandline_args += ["--attach=%d" % attach_pid]
+
+        libc = ctypes.CDLL(None)
+        libc.ptsname.argtypes = (ctypes.c_int,)
+        libc.ptsname.restype = ctypes.c_char_p
+        pty_path = libc.ptsname(self._master.fileno()).decode()
+        commandline_args += ["serial://%s" % (pty_path,)]
+        return commandline_args
+
+    def connect_to_debug_monitor(self, attach_pid=None):
+        self.reverse_connect = False
+        server = self.launch_debug_monitor(attach_pid=attach_pid)
+        self.assertIsNotNone(server)
+
+        # TODO: make it into proper abstraction
+        class FakeSocket:
+            def __init__(self, fd):
+                self.fd = fd
+
+            def sendall(self, frame):
+                self.fd.write(frame)
+
+            def recv(self, count):
+                return self.fd.read(count)
+
+        self.sock = FakeSocket(self._master)
+        self._server = Server(self.sock, server)
+        return server
+
+    @add_test_categories(["llgs"])
+    def test_pty_server(self):
+        self.build()
+        self.set_inferior_startup_launch()
+        self.prep_debug_monitor_and_inferior()
+
+        # target.xml transfer should trigger a large enough packet to check
+        # for partial write regression
+        self.test_sequence.add_log_lines([
+            "read packet: $qXfer:features:read:target.xml:0,200000#00",
+            {
+                "direction": "send",
+                "regex": re.compile("^\$l(.+)#[0-9a-fA-F]{2}$"),
+                "capture": {1: "target_xml"},
+            }],
+            True)
+        context = self.expect_gdbremote_sequence()
+        # verify that we have received a complete, non-malformed XML
+        self.assertIsNotNone(ET.fromstring(context.get("target_xml")))
Index: lldb/tools/lldb-server/lldb-gdbserver.cpp
===================================================================
--- lldb/tools/lldb-server/lldb-gdbserver.cpp
+++ lldb/tools/lldb-server/lldb-gdbserver.cpp
@@ -230,24 +230,27 @@
       final_host_and_port.append("localhost");
     final_host_and_port.append(host_and_port.str());
 
-    if (reverse_connect) {
+    bool is_url = host_and_port.contains("://");
+    if (reverse_connect || is_url) {
       // llgs will connect to the gdb-remote client.
 
-      // Ensure we have a port number for the connection.
-      // Note: use rfind, because the host/port may look like "[::1]:12345".
-      uint32_t connection_portno = 0;
-      const std::string::size_type colon_pos = final_host_and_port.rfind(':');
-      if (colon_pos != std::string::npos)
-        llvm::to_integer(final_host_and_port.substr(colon_pos + 1),
-                         connection_portno);
-      if (connection_portno == 0) {
-        llvm::errs() << "error: port number must be specified on when using "
-                        "reverse connect\n";
-        exit(1);
-      }
+      if (!is_url) {
+        // Ensure we have a port number for the connection.
+        // Note: use rfind, because the host/port may look like "[::1]:12345".
+        uint32_t connection_portno = 0;
+        const std::string::size_type colon_pos = final_host_and_port.rfind(':');
+        if (colon_pos != std::string::npos)
+          llvm::to_integer(final_host_and_port.substr(colon_pos + 1),
+                           connection_portno);
+        if (connection_portno == 0) {
+          llvm::errs() << "error: port number must be specified on when using "
+                          "reverse connect\n";
+          exit(1);
+        }
 
-      // Build the connection string.
-      final_host_and_port.insert(0, "connect://");
+        // Build the connection string.
+        final_host_and_port.insert(0, "connect://");
+      }
 
       // Create the connection.
       connection_up.reset(new ConnectionFileDescriptor);