debugger disconnect on embed mono

[johnson3d]

I embed mono by options:

const char* options[] = {
"--soft-breakpoints",
"--debugger-agent=transport=dt_socket,server=y,address=127.0.0.1:55555,timeout=9999999"
};
mono_jit_parse_options(sizeof(options) / sizeof(char*), (char**)options);

mono_debug_init(MONO_DEBUG_FORMAT_MONO);

mono debug can accept this socket ,but debug thread will get a disconnect event soon, then thread will exit:
res = transport_recv (header, HEADER_LENGTH);

	/* This will break if the socket is closed during shutdown too */
	if (res != HEADER_LENGTH) {
		PRINT_DEBUG_MSG (1, "[dbg] transport_recv () returned %d, expected %d.\n", res, HEADER_LENGTH);

this is the launch.json:
{
// Use IntelliSense to learn about possible attributes.
// Hover to view descriptions of existing attributes.
// For more information, visit: https://go.microsoft.com/fwlink/?linkid=830387
"version": "0.2.0",
"configurations": [
{
"name": "Launch",
"type": "mono",
"request": "launch",
"program": "F:/TProject/Module/CSharpTestMono/bin/Debug/CSharpTestMono.exe",//"${workspaceRoot}/program.exe",
"cwd": "F:/TProject/Module/EmbedMono/x64/Debug"//"${workspaceRoot}"
},
{
"name": "Attach",
"type": "mono",
"request": "attach",
"address": "localhost",
"port": 55555,
},
]
}

I can debug by Launch,But Attach is not ok now.