SFTP/FTP connection timeouts when left unused for few minutes

I am running Linux Mint 20.1 Ulyssa (Xfce 4.14.2) and I have this issue where I am programming something using SFTP/FTP connection through Thunar, and if I stay too long without editing/modifying/saving any files through SFTP connection, it will disconnect me, meaning I need to unmount the "directory" and then connect again.

The way I have connected to my SFTP/FTP is that I simply just go from my Thunar to Go->Open Location and write my SFTP/FTP connection string there sftp://ip-here/. I have it saved(/mounted?) currently, so I don't need to write it anymore, making it easier for me to just double-click the directory to open it.

I have tried to tweak my SSH config increasing the ServerAliveInterval and ServerAliveCountMax to 1 hour, but this seems to have no effect.

How can I increase the timeout time, so it would not disconnect me from the server too often?

Server's SSH settings

# $OpenBSD: sshd_config,v 1.103 2018/04/09 20:41:22 tj Exp $
# This is the sshd server system-wide configuration file. See
# sshd_config(5) for more information.
# This sshd was compiled with PATH=/usr/bin:/bin:/usr/sbin:/sbin
# The strategy used for options in the default sshd_config shipped with
# OpenSSH is to specify options with their default value where
# possible, but leave them commented. Uncommented options override the
# default value.
#Port 22
#AddressFamily any
#ListenAddress 0.0.0.0
#ListenAddress ::
#HostKey /etc/ssh/ssh_host_rsa_key
#HostKey /etc/ssh/ssh_host_ecdsa_key
#HostKey /etc/ssh/ssh_host_ed25519_key
# Ciphers and keying
#RekeyLimit default none
# Logging
#SyslogFacility AUTH
#LogLevel INFO
# Authentication:
#LoginGraceTime 2m
#PermitRootLogin prohibit-password
#StrictModes yes
#MaxAuthTries 6
#MaxSessions 10
#PubkeyAuthentication yes
# Expect .ssh/authorized_keys2 to be disregarded by default in future.
#AuthorizedKeysFile .ssh/authorized_keys .ssh/authorized_keys2
#AuthorizedPrincipalsFile none
#AuthorizedKeysCommand none
#AuthorizedKeysCommandUser nobody
# For this to work you will also need host keys in /etc/ssh/ssh_known_hosts
#HostbasedAuthentication no
# Change to yes if you don't trust ~/.ssh/known_hosts for
# HostbasedAuthentication
#IgnoreUserKnownHosts no
# Don't read the user's ~/.rhosts and ~/.shosts files
#IgnoreRhosts yes
# To disable tunneled clear text passwords, change to no here!
#PasswordAuthentication yes

My computer's SSH settings

Host *
# ForwardAgent no
# ForwardX11 no
# ForwardX11Trusted yes
# PasswordAuthentication yes
# HostbasedAuthentication no
# GSSAPIAuthentication no
# GSSAPIDelegateCredentials no
# GSSAPIKeyExchange no
# GSSAPITrustDNS no
# BatchMode no
# CheckHostIP yes
# AddressFamily any
# ConnectTimeout 0
# StrictHostKeyChecking ask
# IdentityFile ~/.ssh/id_rsa
# IdentityFile ~/.ssh/id_dsa
# IdentityFile ~/.ssh/id_ecdsa
# IdentityFile ~/.ssh/id_ed25519
# Port 22
# Ciphers aes128-ctr,aes192-ctr,aes256-ctr,aes128-cbc,3des-cbc
# MACs hmac-md5,hmac-sha1,
# EscapeChar ~
# Tunnel no
# TunnelDevice any:any
# PermitLocalCommand no
# VisualHostKey no
# ProxyCommand ssh -q -W %h:%p gateway.example.com
# RekeyLimit 1G 1h SendEnv LANG LC_* HashKnownHosts yes GSSAPIAuthentication yes ServerAliveInterval 300 ServerAliveCountMax 3

2 Answers

You could be hitting a NAT timeout or something strange. Others noted the use of ClientAliveInterval and ClientAliveCountMax in the comments. This is what my config has been using for years:

ServerAliveInterval 45
ServerAliveCountMax 60

On the server side you could try this:

ClientAliveInterval 60
TCPKeepAlive yes

Also see this in another SE community:

If it is a problem with Thonar, then try the SSHFS FUSE filesystem:

• sudo apt-get install sshfs
• sshfs-mount -o reconnect user@remotehost:/some/dir/ /home/me/mountpoint/

If you use SSH keys for authentication then -o reconnect will work great. If not, leave off -o reconnect.

Note that once sshfs has mounted you can use it like a normal filesystem, so no need to use sftp:// locations.