How to fix client_loop: send disconnect: Broken pipe in SSH

Configure your SSH client to send keepalive packets every 60 seconds. Add to ~/.ssh/config:

Host *
    ServerAliveInterval 60
    ServerAliveCountMax 3

This tells your SSH client to send a null packet every 60 seconds to keep the connection alive. ServerAliveCountMax 3 means it will retry 3 times before giving up (total: 180 seconds of no response).

Alternatively, use on command-line for one-off connections:

ssh -o ServerAliveInterval=60 user@hostname

This is the most reliable client-side fix and works immediately without server changes.

Add TCPKeepAlive to your SSH config to send TCP-level keepalives:

Host *
    ServerAliveInterval 60
    ServerAliveCountMax 3
    TCPKeepAlive yes

TCPKeepAlive uses lower-level TCP keepalive probes. Combined with ServerAliveInterval, this provides redundant keepalive mechanisms and is especially useful if SSH-level keepalives alone aren't working.

If you have access to the SSH server, configure server-side keepalive settings. Edit /etc/ssh/sshd_config:

sudo nano /etc/ssh/sshd_config

Add or update:

ClientAliveInterval 300
ClientAliveCountMax 3

This tells the server to send a keepalive packet every 300 seconds (5 minutes) if no activity from client, retrying 3 times.

After editing, restart SSH service:

sudo systemctl restart sshd

ServerAliveInterval on the client is usually enough, but server-side config helps when many clients connect with stale settings.

If you experience disconnects on a specific network (VPN, corporate firewall), reduce the ServerAliveInterval to send packets more frequently:

Host restrictive-network
    ServerAliveInterval 30
    ServerAliveCountMax 5
    TCPKeepAlive yes

This sends keepalive packets every 30 seconds (instead of 60), which stays ahead of aggressive firewall timeouts (typically 5-15 minutes).

For particularly troublesome networks:

Host very-restrictive
    ServerAliveInterval 20
    ServerAliveCountMax 3
    TCPKeepAlive yes
    ExitOnForwardFailure yes

Lower intervals use slightly more bandwidth but guarantee the connection never sits idle.

If SSH keepalive settings don't solve the problem (especially for mobile/WiFi), consider using mosh (mobile shell):

sudo apt-get install mosh  # Debian/Ubuntu
sudo yum install mosh      # RHEL/CentOS
brew install mosh          # macOS

Then connect:

mosh user@hostname

Mosh is designed for mobile/unreliable connections:
- Tolerates network changes (WiFi to cellular)
- Automatically reconnects on temporary network loss
- Lower bandwidth usage
- Supports disconnecting/reconnecting without losing session

Mosh runs on top of SSH, so your server still needs SSH; it's a better shell for roaming connections.

If keepalive settings don't resolve the issue, your network may have aggressive filtering:

# Test if packets are actually being sent
ssh -vv user@hostname

Look for lines like "Sending SSH2_MSG_IGNORE" or "Packet type..." which confirm keepalive is active.

If still disconnecting:
- Check if you're behind a corporate proxy (ask your network admin)
- Test on a different network (home WiFi, cellular hotspot, VPN)
- Contact your ISP if it's a home internet issue
- For cloud VMs, check the security group/firewall rules allow outbound SSH

If behind a proxy:

Host proxy-host
    ProxyCommand ssh bastion-host 'nc %h %p'
    ServerAliveInterval 60

Ensure keepalive settings are on both the client and bastion connections.