When working with StatsD and trying to stream metrics through netcat in UDP mode, many developers encounter an annoying behavior: the process hangs even after specifying -q 0. This happens because:

printf "folder.counter:value|1c" | nc -q 0 -u statsd.example.com 8125
# Process hangs here waiting for more input

The -w timeout option presents its own challenges:

• Setting -w 1 causes buffer buildup during high-frequency writes
• Smaller timeout values risk packet loss
• The fundamental issue stems from how netcat handles UDP EOF

Here are three effective approaches I've used in production environments:

# Solution 1: Use socat instead
printf "folder.counter:value|1c" | socat - udp:statsd.example.com:8125

# Solution 2: Force close with bash redirection
(printf "folder.counter:value|1c"; sleep 0.1) > /dev/udp/statsd.example.com/8125

# Solution 3: Python fallback (when you need reliability)
import socket
sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
sock.sendto(b"folder.counter:value|1c", ("statsd.example.com", 8125))

The hanging behavior occurs because:

1. UDP is connectionless - no EOF concept exists in the protocol
2. Netcat's -q implementation primarily works for TCP streams
3. The kernel buffers the UDP packet but netcat keeps waiting for more data

For high-volume StatsD environments, I recommend this bash pattern:

while read -r line; do
  {
    printf "%s" "$line" > /dev/udp/localhost/8125 &
    disown
  } 2>/dev/null
done

The key improvements are:

• Background process (&) prevents blocking
• disown prevents zombie processes
• Error suppression handles potential network issues

For mission-critical monitoring:

• Use official StatsD client libraries (Node.js, Python, Java)
• Implement queuing with Redis for spike protection
• Consider Telegraf as a metrics agent alternative

When using netcat (nc) in UDP mode to send StatsD metrics, the command hangs indefinitely despite using -q 0 flag. This behavior persists even with timeout flags (-w), causing buffer buildup when sending multiple metrics.

Unlike TCP, UDP is connectionless by design. Netcat's -q flag primarily works for TCP connections where EOF can be properly detected. In UDP mode:

• There's no connection termination signal
• The operating system doesn't guarantee packet delivery
• Netcat has no way to know when to stop waiting

Here are three practical approaches to solve this:

1. Using socat Instead

while read line; do
    echo "folder.counter:value|1c" | socat - udp:$host:$port
done

2. Proper Netcat Implementation

while read line; do
    echo "folder.counter:value|1c" > /dev/udp/$host/$port
done

3. Native Bash UDP Support

while read line; do
    echo -n "folder.counter:value|1c" > /dev/udp/$host/$port
done

For high-throughput StatsD implementations:

• Batch metrics when possible
• Consider direct UDP socket programming in Python/Node.js
• Implement proper error handling for dropped packets

import socket

sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)

while True:
    metric = input()
    sock.sendto(f"{metric}|1c".encode(), (host, port))

• Netcat's UDP behavior differs from TCP
• Alternative tools (socat) handle UDP better
• Modern shells have built-in UDP support
• For production, consider proper StatsD client libraries