Communication between YARP server on a host machine and a Docker container

[PeterBowman]

Hello. I am unable to connect ports between a YARP server running on the host machine and a Docker container. So far, I have tested https://hub.docker.com/r/robotology/yarp (running a quite old YARP 3.1) and also a custom image built with YARP 3.9, enabling ports in this manner:

docker run --rm -it --network host --privileged --pid host -v /etc/hosts:/etc/hosts robotology/yarp /bin/bash

I have properly configured the conf file, so that yarp detect and yarp name list work. Then, I opened a yarp read port on the host and a yarp write port in the container (also tried the other way round). Upon connecting them with:

YARP_VERBOSE=1 yarp connect /write /read

I get (several debug lines have been redacted out):

[DEBUG] |yarp.os.Network| asking tcp://write: [list] [out] "/read"
[ERROR] |yarp.os.impl.TcpConnector.posix| Connect [handle=3] at 192.168.0.69:4647
[DEBUG] |yarp.os.impl.SocketTwoWayStream| TCP connection to tcp://192.168.0.69:10002/ failed to open
[ERROR] |yarp.os.impl.SocketTwoWayStream| SocketTwoWayStream::updateAddresses failed getting local address
[DEBUG] |yarp.os.impl.SocketTwoWayStream| updateAddresses: local address = 192.168.0.69
[DEBUG] |yarp.os.impl.SocketTwoWayStream| updateAddresses: remote address = 
[ERROR] |yarp.os.Network| Cannot connect to port /write
[DEBUG] |yarp.os.impl.NameClient| sending to nameserver: NAME_SERVER announce /write 0
[DEBUG] |yarp.os.impl.NameClient| connecting to /192.168.0.69:10000/
[DEBUG] |yarp.os.impl.SocketTwoWayStream| updateAddresses: local address = 192.168.0.69
[DEBUG] |yarp.os.impl.SocketTwoWayStream| updateAddresses: remote address = 192.168.0.69
[DEBUG] |yarp.os.impl.Protocol| Remote contact = 
[DEBUG] |yarp.os.impl.NameClient| <<< received from nameserver: [ok]

What am I doing wrong?

[PeterBowman]

So far I have narrowed it down to a "[111] Connection refused" error (replacing line 112 with printf("[%d] %s\n", valopt, strerror(valopt));):

yarp/src/libYARP_os/src/yarp/os/impl/posix/TcpConnector.cpp

Lines 91 to 133 in bde9cd2

	// Trying to connect with timeout
	res = ::connect(handle, reinterpret_cast<sockaddr*>(&servAddr), sizeof(servAddr));
	if (res < 0) {
	if (errno == EINPROGRESS) {
	FD_ZERO(&myset);
	FD_SET(handle, &myset);
	res = select(handle + 1, nullptr, &myset, nullptr, timeout);
	if (res < 0 && errno != EINTR) {
	yCError(TCPCONNECTOR_POSIX, "connect fail: Error connecting: %d, %s", errno, strerror(errno));
	res = -1;
	} else if (res > 0) {
	res = 0;
	// Socket selected for write
	lon = sizeof(int);
	if (getsockopt(handle, SOL_SOCKET, SO_ERROR, reinterpret_cast<void*>(&valopt), &lon) < 0) {
	yCError(TCPCONNECTOR_POSIX, "connect fail: Error in getsockopt(): %d, %s", errno, strerror(errno));
	res = -1;
	}
	// Check the value returned...
	if (valopt) {
	// connect fail: Error in delayed connection() -> the port doesn't exist
	res = -1;
	}
	} else {
	yCError(TCPCONNECTOR_POSIX, "connect fail: Timeout in select() - Cancelling!: %d, %s", errno, strerror(errno));
	res = -1;
	}
	} else {
	yCError(TCPCONNECTOR_POSIX, "connect fail: Error connecting: %d, %s", errno, strerror(errno));
	res = -1;
	}
	}
	if (res != 0) {
	char buf[INET_ADDRSTRLEN];
	yCError(TCPCONNECTOR_POSIX,
	"Connect [handle=%d] at %s:%d",
	new_stream.get_handle(),
	inet_ntop(AF_INET, &servAddr.sin_addr, buf, INET_ADDRSTRLEN),
	servAddr.sin_port);;
	return -1;
	}

[PeterBowman]

Solved, I have been using Rootless Docker and probably hit some if its known limitations. I switched to using Docker as a non-sudo user and it worked, even without the need of --network host. Thanks @jgvictores @imontesino!