$ strace -p PID
epoll_ctl(4, EPOLL_CTL_MOD, 17, {EPOLLIN, {u32=17, u64=69435872986005521}}) = 0
epoll_pwait(4, {{EPOLLIN|EPOLLHUP, {u32=17, u64=69435872986005521}}}, 1024, 123, NULL, 8) = 1
epoll_ctl(4, EPOLL_CTL_MOD, 17, {EPOLLIN, {u32=17, u64=69435872986005521}}) = 0
epoll_pwait(4, {{EPOLLIN|EPOLLHUP, {u32=17, u64=69435872986005521}}}, 1024, 123, NULL, 8) = 1
epoll_ctl(4, EPOLL_CTL_MOD, 17, {EPOLLIN, {u32=17, u64=69435872986005521}}) = 0
epoll_pwait(4, {{EPOLLIN|EPOLLHUP, {u32=17, u64=69435872986005521}}}, 1024, 122, NULL, 8) = 1
epoll_ctl(4, EPOLL_CTL_MOD, 17, {EPOLLIN, {u32=17, u64=69435872986005521}}) = 0
epoll_pwait(4, {{EPOLLIN|EPOLLHUP, {u32=17, u64=69435872986005521}}}, 1024, 122, NULL, 8) = 1
epoll_ctl(4, EPOLL_CTL_MOD, 17, {EPOLLIN, {u32=17, u64=69435872986005521}}) = 0
epoll_pwait(4, {{EPOLLIN|EPOLLHUP, {u32=17, u64=69435872986005521}}}, 1024, 122, NULL, 8) = 1
epoll_ctl(4, EPOLL_CTL_MOD, 17, {EPOLLIN, {u32=17, u64=69435872986005521}}) = 0
epoll_pwait(4, {{EPOLLIN|EPOLLHUP, {u32=17, u64=69435872986005521}}}, 1024, 122, NULL, 8) = 1
epoll_ctl(4, EPOLL_CTL_MOD, 17, {EPOLLIN, {u32=17, u64=69435872986005521}}) = 0
epoll_pwait(4, {{EPOLLIN|EPOLLHUP, {u32=17, u64=69435872986005521}}}, 1024, 122, NULL, 8) = 1
epoll_ctl(4, EPOLL_CTL_MOD, 17, {EPOLLIN, {u32=17, u64=69435872986005521}}) = 0
epoll_pwait(4, {{EPOLLIN|EPOLLHUP, {u32=17, u64=69435872986005521}}}, 1024, 122, NULL, 8) = 1
epoll_ctl(4, EPOLL_CTL_MOD, 17, {EPOLLIN, {u32=17, u64=69435872986005521}}) = 0
epoll_pwait(4, {{EPOLLIN|EPOLLHUP, {u32=17, u64=69435872986005521}}}, 1024, 122, NULL, 8) = 1
epoll_ctl(4, EPOLL_CTL_MOD, 17, {EPOLLIN, {u32=17, u64=69435872986005521}}) = 0
epoll_pwait(4, {{EPOLLIN|EPOLLHUP, {u32=17, u64=69435872986005521}}}, 1024, 122, NULL, 8) = 1
epoll_ctl(4, EPOLL_CTL_MOD, 17, {EPOLLIN, {u32=17, u64=69435872986005521}}) = 0
epoll_pwait(4, {{EPOLLIN|EPOLLHUP, {u32=17, u64=69435872986005521}}}, 1024, 122, NULL, 8) = 1
epoll_ctl(4, EPOLL_CTL_MOD, 17, {EPOLLIN, {u32=17, u64=69435872986005521}}) = 0
epoll_pwait(4, {{EPOLLIN|EPOLLHUP, {u32=17, u64=69435872986005521}}}, 1024, 122, NULL, 8) = 1
epoll_ctl(4, EPOLL_CTL_MOD, 17, {EPOLLIN, {u32=17, u64=69435872986005521}}) = 0
epoll_pwait(4, {{EPOLLIN|EPOLLHUP, {u32=17, u64=69435872986005521}}}, 1024, 122, NULL, 8) = 1
epoll_ctl(4, EPOLL_CTL_MOD, 17, {EPOLLIN, {u32=17, u64=69435872986005521}}) = 0
epoll_pwait(4, {{EPOLLIN|EPOLLHUP, {u32=17, u64=69435872986005521}}}, 1024, 122, NULL, 8) = 1
^CProcess 517 detached

$ lsof -d 17
COMMAND PID USER   FD   TYPE             DEVICE SIZE/OFF      NODE NAME
node    517 root   17u  unix 0xffff881057cb2000      0t0 760434497 socket