You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: server.rs
    path of file: ./repos/PumpkinDB/pumpkindb_mio_server/src
    
    the code of the file until where you have to start completion: // Copyright (c) 2017, All Contributors (see CONTRIBUTORS file)
//
// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this
// file, You can obtain one at http://mozilla.org/MPL/2.0/.

use std::io;
use std::rc::Rc;
use std::sync::mpsc;
use std::collections::BTreeMap;

use slab;
use mio::channel as mio_chan;
use mio::*;
use mio::tcp::*;

use super::connection::Connection;

type Slab<T> = slab::Slab<T, Token>;

use pumpkindb_engine::messaging;
use pumpkindb_engine::script::{EnvId, Sender, RequestMessage, ResponseMessage, SchedulerHandle};

use uuid::Uuid;

pub type RelayedPublishedMessage = (Vec<u8>, Vec<u8>, Vec<u8>);

struct RelayedPublishedMessageSender {
    identifier: Vec<u8>,
    sender: mio_ch
    
    fn accept(&mut self, poll: &mut Poll) {
        loop {
            let sock = match self.sock.accept() {
                Ok((sock, _)) => sock,
                Err(_) => return,
            };

            let token = match self.conns.vacant_entry() {
                Some(entry) => {
                    let c = Connection::new(sock, entry.index());
                    entry.insert(c).index()
                }
                None => return,
            };

            match self.find_connection_by_token(token).register(poll) {
                Ok(_) => {
                    let session = Vec::from(&Uuid::new_v4().as_bytes()[..]);
                    self.session_token.insert(session.clone(), token);
                    self.token_session.insert(token, session);
                }
                Err(_) => {
                    self.conns.remove(token);
                }
            }
        }
    }