nc와 fifo의 이상하고 일관되지 않은 출력

나는 다음과 같은 정확한 코드를 가지고 있습니다.

#!/bin/bash

gtimeout(){
  if type -f gtimeout &> /dev/null; then
    command gtimeout "$@"
  else
    timeout "$@"
  fi
}

export -f gtimeout;


on_first_match(){
   local pattern="$1"  # The pattern to search for
    while IFS= read -r line; do
        if [[ "$line" == *"$pattern"* ]]; then
            exit 0
        fi
    done
}

export -f on_first_match


write_to_server(){
  echo -e "$?" | nc 0.0.0.0 3333
}

export -f write_to_server

(

set +e;
sleep 2;

  (
     gtimeout 15 docker logs -f rabbitmq-node1 | on_first_match 'Starting listener on';
     write_to_server
  ) &


  (
    gtimeout 15 docker logs -f mongodb-node1 | on_first_match 'waiting for connections';
    write_to_server
  ) &


  (
    gtimeout 15 docker logs -f elasticsearch-node1 | on_first_match 'started';
    write_to_server
  ) &


  (
     gtimeout 15 docker logs -f rabbitmq-node2 | on_first_match 'Starting listener on';
     write_to_server
  ) &


  (
    gtimeout 15 docker logs -f mongodb-node2 | on_first_match 'waiting for connections';
    write_to_server
  ) &


  (
    gtimeout 15 docker logs -f elasticsearch-node2 | on_first_match 'started';
    write_to_server
  ) &


  (
     gtimeout 15 docker logs -f rabbitmq-node3 | on_first_match 'Starting listener on';
     write_to_server
  ) &


  (
    gtimeout 15 docker logs -f mongodb-node3 | on_first_match 'waiting for connections';
    write_to_server
  ) &


  (
    gtimeout 15 docker logs -f elasticsearch-node3 | on_first_match 'started';
    write_to_server
  ) &


) &

gtimeout 30 nc -k -l 3333 | while IFS= read -r line; do
      echo "Received: $line";
done

내가 얻는 결과는 다음과 같습니다.

Error response from daemon: No such container: mongodb-node1
Error response from daemon: No such container: rabbitmq-node2
Error response from daemon: No such container: rabbitmq-node1
Error response from daemon: No such container: elasticsearch-node2
Error response from daemon: No such container: elasticsearch-node1
Error response from daemon: No such container: mongodb-node2
Error response from daemon: No such container: mongodb-node3
Error response from daemon: No such container: rabbitmq-node3
Error response from daemon: No such container: elasticsearch-node3
Received: 0
Received: 0
Received: 0
Received: 0
Received: 0

(5줄만 수신되고 때로는 4줄, 때로는 6줄이 수신되지만 예상대로 9줄은 수신되지 않음)

하지만 나는 이것을 기대한다:

Error response from daemon: No such container: mongodb-node1
Error response from daemon: No such container: rabbitmq-node2
Error response from daemon: No such container: rabbitmq-node1
Error response from daemon: No such container: elasticsearch-node2
Error response from daemon: No such container: elasticsearch-node1
Error response from daemon: No such container: mongodb-node2
Error response from daemon: No such container: mongodb-node3
Error response from daemon: No such container: rabbitmq-node3
Error response from daemon: No such container: elasticsearch-node3
Received: 0
Received: 0
Received: 0
Received: 0
Received: 0
Received: 0
Received: 0
Received: 0
Received: 0

9개의 수신 라인이 있습니다.

무슨 일인지 아는 사람 있나요? (소켓 대신 mkfifo로 코드를 전환하면 동일한 동작이 발생합니다).