Connectivity Issue with UrBackup Client Not Accepting Connections from Server

Hello Community,

I am facing an issue with the UrBackup client on my network where the client is not accepting connections from the UrBackup server. I have the UrBackup client installed on a Linux machine and the server on a Windows machine. Both systems are within the same local network.

Client Version:

 $ sudo urbackupclientbackend --version
UrBackup Client Backend v2.5.25.0
Copyright (C) 2011-2019 Martin Raiber
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

Server (UrBackup 2.5.33) to Client:

PS D:\UrBackupServer> @(55413, 55414, 55415, 35623).ForEach({ Test-NetConnection -ComputerName "chuwi" -Port $_ | Select-Object ComputerName, TcpTestSucceeded, RemotePort })
WARNUNG: TCP connect to (192.168.178.173 : 55413) failed
WARNUNG: TCP connect to (192.168.178.173 : 55414) failed
WARNUNG: TCP connect to (192.168.178.173 : 55415) failed
WARNUNG: TCP connect to (192.168.178.173 : 35623) failed

ComputerName TcpTestSucceeded RemotePort
------------ ---------------- ----------
chuwi                   False      55413
chuwi                   False      55414
chuwi                   False      55415
chuwi                   False      35623

Client to Server:

$ sudo nmap -sT desktop-6p79g8t.local -p 55413,55414,55415,35623
Starting Nmap 7.80 ( https://nmap.org ) at 2024-05-13 18:39 UTC
Nmap scan report for desktop-6p79g8t.local (192.168.178.162)
Host is up (0.0028s latency).
rDNS record for 192.168.178.162: DESKTOP-6P79G8T.local

PORT      STATE    SERVICE
35623/tcp filtered unknown
55413/tcp open     unknown
55414/tcp open     unknown
55415/tcp open     unknown
MAC Address: D8:BB:C1:43:13:90 (Unknown)

tcpdump Protocoll:

$ sudo tcpdump -i any 'tcp port (55413 or 55414 or 55415 or 35623) or udp port 35622'
tcpdump: data link type LINUX_SLL2
tcpdump: verbose output suppressed, use -v[v]... for full protocol decode
listening on any, link-type LINUX_SLL2 (Linux cooked v2), snapshot length 262144 bytes
18:49:50.390927 enp1s0 In  IP DESKTOP-6P79G8T.local.44282 > chuwi.local.55413: Flags [S], seq 428408656, win 64240, options [mss 1460,nop,wscale 8,nop,nop,sackOK], length 0
18:49:50.391064 enp1s0 Out IP chuwi.local.55413 > DESKTOP-6P79G8T.local.44282: Flags [R.], seq 0, ack 428408657, win 0, length 0
18:49:50.912775 enp1s0 In  IP DESKTOP-6P79G8T.local.44282 > chuwi.local.55413: Flags [S], seq 428408656, win 64240, options [mss 1460,nop,wscale 8,nop,nop,sackOK], length 0
18:49:50.912899 enp1s0 Out IP chuwi.local.55413 > DESKTOP-6P79G8T.local.44282: Flags [R.], seq 0, ack 1, win 0, length 0
18:49:51.432293 enp1s0 In  IP DESKTOP-6P79G8T.local.44282 > chuwi.local.55413: Flags [S], seq 428408656, win 64240, options [mss 1460,nop,wscale 8,nop,nop,sackOK], length 0
18:49:51.432433 enp1s0 Out IP chuwi.local.55413 > DESKTOP-6P79G8T.local.44282: Flags [R.], seq 0, ack 1, win 0, length 0
18:49:51.951284 enp1s0 In  IP DESKTOP-6P79G8T.local.44282 > chuwi.local.55413: Flags [S], seq 428408656, win 64240, options [mss 1460,nop,wscale 8,nop,nop,sackOK], length 0
18:49:51.951429 enp1s0 Out IP chuwi.local.55413 > DESKTOP-6P79G8T.local.44282: Flags [R.], seq 0, ack 1, win 0, length 0
18:49:52.454016 enp1s0 In  IP DESKTOP-6P79G8T.local.44282 > chuwi.local.55413: Flags [S], seq 428408656, win 64240, options [mss 1460,nop,wscale 8,nop,nop,sackOK], length 0
18:49:52.454144 enp1s0 Out IP chuwi.local.55413 > DESKTOP-6P79G8T.local.44282: Flags [R.], seq 0, ack 1, win 0, length 0
18:49:55.452420 enp1s0 In  IP DESKTOP-6P79G8T.local.44283 > chuwi.local.55414: Flags [S], seq 3909549676, win 64240, options [mss 1460,nop,wscale 8,nop,nop,sackOK], length 0
18:49:55.452545 enp1s0 Out IP chuwi.local.55414 > DESKTOP-6P79G8T.local.44283: Flags [R.], seq 0, ack 3909549677, win 0, length 0
18:49:55.968389 enp1s0 In  IP DESKTOP-6P79G8T.local.44283 > chuwi.local.55414: Flags [S], seq 3909549676, win 64240, options [mss 1460,nop,wscale 8,nop,nop,sackOK], length 0
18:49:55.968509 enp1s0 Out IP chuwi.local.55414 > DESKTOP-6P79G8T.local.44283: Flags [R.], seq 0, ack 1, win 0, length 0
18:49:56.480303 enp1s0 In  IP DESKTOP-6P79G8T.local.44283 > chuwi.local.55414: Flags [S], seq 3909549676, win 64240, options [mss 1460,nop,wscale 8,nop,nop,sackOK], length 0
18:49:56.480439 enp1s0 Out IP chuwi.local.55414 > DESKTOP-6P79G8T.local.44283: Flags [R.], seq 0, ack 1, win 0, length 0
18:49:56.999605 enp1s0 In  IP DESKTOP-6P79G8T.local.44283 > chuwi.local.55414: Flags [S], seq 3909549676, win 64240, options [mss 1460,nop,wscale 8,nop,nop,sackOK], length 0
18:49:56.999750 enp1s0 Out IP chuwi.local.55414 > DESKTOP-6P79G8T.local.44283: Flags [R.], seq 0, ack 1, win 0, length 0
18:49:57.523793 enp1s0 In  IP DESKTOP-6P79G8T.local.44283 > chuwi.local.55414: Flags [S], seq 3909549676, win 64240, options [mss 1460,nop,wscale 8,nop,nop,sackOK], length 0
18:49:57.523919 enp1s0 Out IP chuwi.local.55414 > DESKTOP-6P79G8T.local.44283: Flags [R.], seq 0, ack 1, win 0, length 0
18:50:00.360157 enp1s0 In  IP DESKTOP-6P79G8T.local.44287 > chuwi.local.55415: Flags [S], seq 3527866430, win 64240, options [mss 1460,nop,wscale 8,nop,nop,sackOK], length 0
18:50:00.360287 enp1s0 Out IP chuwi.local.55415 > DESKTOP-6P79G8T.local.44287: Flags [R.], seq 0, ack 3527866431, win 0, length 0
18:50:00.868454 enp1s0 In  IP DESKTOP-6P79G8T.local.44287 > chuwi.local.55415: Flags [S], seq 3527866430, win 64240, options [mss 1460,nop,wscale 8,nop,nop,sackOK], length 0
18:50:00.868591 enp1s0 Out IP chuwi.local.55415 > DESKTOP-6P79G8T.local.44287: Flags [R.], seq 0, ack 1, win 0, length 0
18:50:01.388394 enp1s0 In  IP DESKTOP-6P79G8T.local.44287 > chuwi.local.55415: Flags [S], seq 3527866430, win 64240, options [mss 1460,nop,wscale 8,nop,nop,sackOK], length 0
18:50:01.388524 enp1s0 Out IP chuwi.local.55415 > DESKTOP-6P79G8T.local.44287: Flags [R.], seq 0, ack 1, win 0, length 0
18:50:01.908445 enp1s0 In  IP DESKTOP-6P79G8T.local.44287 > chuwi.local.55415: Flags [S], seq 3527866430, win 64240, options [mss 1460,nop,wscale 8,nop,nop,sackOK], length 0
18:50:01.908578 enp1s0 Out IP chuwi.local.55415 > DESKTOP-6P79G8T.local.44287: Flags [R.], seq 0, ack 1, win 0, length 0
18:50:02.416310 enp1s0 In  IP DESKTOP-6P79G8T.local.44287 > chuwi.local.55415: Flags [S], seq 3527866430, win 64240, options [mss 1460,nop,wscale 8,nop,nop,sackOK], length 0
18:50:02.416449 enp1s0 Out IP chuwi.local.55415 > DESKTOP-6P79G8T.local.44287: Flags [R.], seq 0, ack 1, win 0, length 0
18:50:05.222820 enp1s0 In  IP DESKTOP-6P79G8T.local.44288 > chuwi.local.35623: Flags [S], seq 691695993, win 64240, options [mss 1460,nop,wscale 8,nop,nop,sackOK], length 0
18:50:05.222916 enp1s0 Out IP chuwi.local.35623 > DESKTOP-6P79G8T.local.44288: Flags [R.], seq 0, ack 691695994, win 0, length 0
18:50:05.736304 enp1s0 In  IP DESKTOP-6P79G8T.local.44288 > chuwi.local.35623: Flags [S], seq 691695993, win 64240, options [mss 1460,nop,wscale 8,nop,nop,sackOK], length 0
18:50:05.736443 enp1s0 Out IP chuwi.local.35623 > DESKTOP-6P79G8T.local.44288: Flags [R.], seq 0, ack 1, win 0, length 0
18:50:06.257344 enp1s0 In  IP DESKTOP-6P79G8T.local.44288 > chuwi.local.35623: Flags [S], seq 691695993, win 64240, options [mss 1460,nop,wscale 8,nop,nop,sackOK], length 0
18:50:06.257479 enp1s0 Out IP chuwi.local.35623 > DESKTOP-6P79G8T.local.44288: Flags [R.], seq 0, ack 1, win 0, length 0
18:50:06.773077 enp1s0 In  IP DESKTOP-6P79G8T.local.44288 > chuwi.local.35623: Flags [S], seq 691695993, win 64240, options [mss 1460,nop,wscale 8,nop,nop,sackOK], length 0
18:50:06.773168 enp1s0 Out IP chuwi.local.35623 > DESKTOP-6P79G8T.local.44288: Flags [R.], seq 0, ack 1, win 0, length 0
18:50:07.300299 enp1s0 In  IP DESKTOP-6P79G8T.local.44288 > chuwi.local.35623: Flags [S], seq 691695993, win 64240, options [mss 1460,nop,wscale 8,nop,nop,sackOK], length 0
18:50:07.300423 enp1s0 Out IP chuwi.local.35623 > DESKTOP-6P79G8T.local.44288: Flags [R.], seq 0, ack 1, win 0, length 0
18:50:23.044425 enp1s0 B   IP DESKTOP-6P79G8T.local.35623 > 255.255.255.255.35622: UDP, length 1
^C
41 packets captured
42 packets received by filter
0 packets dropped by kernel

Client local Firewall:

$ sudo ufw status verbose
Status: active
Logging: on (low)
Default: deny (incoming), allow (outgoing), deny (routed)
New profiles: skip

To                         Action      From
--                         ------      ----
80,443/tcp (Nginx Full)    ALLOW IN    Anywhere
55413/tcp                  ALLOW IN    Anywhere
55414/tcp                  ALLOW IN    Anywhere
55415/tcp                  ALLOW IN    Anywhere
35623/tcp                  ALLOW IN    Anywhere
35622/udp                  ALLOW IN    Anywhere
7655/tcp                   ALLOW IN    Anywhere
80,443/tcp (Nginx Full (v6)) ALLOW IN    Anywhere (v6)
55413/tcp (v6)             ALLOW IN    Anywhere (v6)
55414/tcp (v6)             ALLOW IN    Anywhere (v6)
55415/tcp (v6)             ALLOW IN    Anywhere (v6)
35623/tcp (v6)             ALLOW IN    Anywhere (v6)
35622/udp (v6)             ALLOW IN    Anywhere (v6)
7655/tcp (v6)              ALLOW IN    Anywhere (v6)

Problem Description:
When I attempt to connect from the Windows server to the Linux client, the connections fail. Using Test-NetConnection from PowerShell on the Windows server indicates that all attempts to the client’s ports are unsuccessful (i.e., TcpTestSucceeded is False). Despite the client machine’s firewall rules allowing the necessary TCP and UDP ports, the server cannot establish a connection.

Technical Details:

  • The UrBackup client is configured to listen on 127.0.0.1 and [::1], which I realized limits it to localhost connections. This setup prevents the server from communicating with the client.
  • When checked with ss -tulnp, it confirms that the client is listening only on localhost for both IPv4 and IPv6.
  • Firewall settings on the client (managed via UFW) are properly configured to allow inbound connections on the required UrBackup ports (55413, 55414, 55415 for TCP and 35623, 35622 for UDP).

Attempts to Resolve:

  • I tried modifying the client configuration to listen on all interfaces by changing 127.0.0.1 to 0.0.0.0 and [::1] to [::], but how?

Does anyone have suggestions on how I might resolve this issue or further steps I can take to diagnose and address this problem effectively? Any advice on how to make the client accept external connections would be greatly appreciated.

I attach some screenshots, mybe it helps



Logs are empty:
image

I try also from Server:

$ sudo urbackupclientctl start --full
Error starting backup. No backup server found.

Thank you for any help you can provide!

Any idea?
From Urbackupserver:

PS C:\Users\User> Test-NetConnection -ComputerName 192.168.178.36 -Port 55413
WARNUNG: TCP connect to (192.168.178.36 : 55413) failed


ComputerName           : 192.168.178.36
RemoteAddress          : 192.168.178.36
RemotePort             : 55413
InterfaceAlias         : Ethernet
SourceAddress          : 192.168.178.162
PingSucceeded          : True
PingReplyDetails (RTT) : 2 ms
TcpTestSucceeded       : False



PS C:\Users\User> Test-NetConnection -ComputerName 192.168.178.36 -Port 55414
WARNUNG: TCP connect to (192.168.178.36 : 55414) failed


ComputerName           : 192.168.178.36
RemoteAddress          : 192.168.178.36
RemotePort             : 55414
InterfaceAlias         : Ethernet
SourceAddress          : 192.168.178.162
PingSucceeded          : True
PingReplyDetails (RTT) : 1 ms
TcpTestSucceeded       : False



PS C:\Users\User>

tcpdump urbackupclient:

$ sudo tcpdump -i any port 55413 or port 55414 -n
tcpdump: data link type LINUX_SLL2
tcpdump: verbose output suppressed, use -v[v]... for full protocol decode
listening on any, link-type LINUX_SLL2 (Linux cooked v2), snapshot length 262144 bytes
23:39:27.579176 enp1s0 In  IP 192.168.178.162.18484 > 192.168.178.36.55413: Flags [S], seq 3137527383, win 64240, options [mss 1460,nop,wscale 8,nop,nop,sackOK], length 0
23:39:27.579326 enp1s0 Out IP 192.168.178.36.55413 > 192.168.178.162.18484: Flags [R.], seq 0, ack 3137527384, win 0, length 0
23:39:28.082452 enp1s0 In  IP 192.168.178.162.18484 > 192.168.178.36.55413: Flags [S], seq 3137527383, win 64240, options [mss 1460,nop,wscale 8,nop,nop,sackOK], length 0
23:39:28.082601 enp1s0 Out IP 192.168.178.36.55413 > 192.168.178.162.18484: Flags [R.], seq 0, ack 1, win 0, length 0
23:39:28.585948 enp1s0 In  IP 192.168.178.162.18484 > 192.168.178.36.55413: Flags [S], seq 3137527383, win 64240, options [mss 1460,nop,wscale 8,nop,nop,sackOK], length 0
23:39:28.586097 enp1s0 Out IP 192.168.178.36.55413 > 192.168.178.162.18484: Flags [R.], seq 0, ack 1, win 0, length 0
23:39:29.092979 enp1s0 In  IP 192.168.178.162.18484 > 192.168.178.36.55413: Flags [S], seq 3137527383, win 64240, options [mss 1460,nop,wscale 8,nop,nop,sackOK], length 0
23:39:29.093128 enp1s0 Out IP 192.168.178.36.55413 > 192.168.178.162.18484: Flags [R.], seq 0, ack 1, win 0, length 0
23:39:29.599406 enp1s0 In  IP 192.168.178.162.18484 > 192.168.178.36.55413: Flags [S], seq 3137527383, win 64240, options [mss 1460,nop,wscale 8,nop,nop,sackOK], length 0
23:39:29.599550 enp1s0 Out IP 192.168.178.36.55413 > 192.168.178.162.18484: Flags [R.], seq 0, ack 1, win 0, length 0
23:39:36.344217 enp1s0 In  IP 192.168.178.162.18485 > 192.168.178.36.55414: Flags [S], seq 1089593205, win 64240, options [mss 1460,nop,wscale 8,nop,nop,sackOK], length 0
23:39:36.344362 enp1s0 Out IP 192.168.178.36.55414 > 192.168.178.162.18485: Flags [R.], seq 0, ack 1089593206, win 0, length 0
23:39:36.859990 enp1s0 In  IP 192.168.178.162.18485 > 192.168.178.36.55414: Flags [S], seq 1089593205, win 64240, options [mss 1460,nop,wscale 8,nop,nop,sackOK], length 0
23:39:36.860141 enp1s0 Out IP 192.168.178.36.55414 > 192.168.178.162.18485: Flags [R.], seq 0, ack 1, win 0, length 0
23:39:37.367407 enp1s0 In  IP 192.168.178.162.18485 > 192.168.178.36.55414: Flags [S], seq 1089593205, win 64240, options [mss 1460,nop,wscale 8,nop,nop,sackOK], length 0
23:39:37.367558 enp1s0 Out IP 192.168.178.36.55414 > 192.168.178.162.18485: Flags [R.], seq 0, ack 1, win 0, length 0
23:39:37.871714 enp1s0 In  IP 192.168.178.162.18485 > 192.168.178.36.55414: Flags [S], seq 1089593205, win 64240, options [mss 1460,nop,wscale 8,nop,nop,sackOK], length 0
23:39:37.871862 enp1s0 Out IP 192.168.178.36.55414 > 192.168.178.162.18485: Flags [R.], seq 0, ack 1, win 0, length 0
23:39:38.376050 enp1s0 In  IP 192.168.178.162.18485 > 192.168.178.36.55414: Flags [S], seq 1089593205, win 64240, options [mss 1460,nop,wscale 8,nop,nop,sackOK], length 0
23:39:38.376200 enp1s0 Out IP 192.168.178.36.55414 > 192.168.178.162.18485: Flags [R.], seq 0, ack 1, win 0, length 0
^C
20 packets captured
22 packets received by filter
0 packets dropped by kernel

netstat

$ sudo netstat -tulnp | grep 5541[34]

is empty