我把Express的代码补充完整试了下，感觉没什么问题啊。

var express = require('express'),
    http = require('http');

var app = express();
app.get('/',function(req,res){
    console.log('request on ' + process.pid);
    res.send('Hello World');
})
var server = http.createServer(app);
console.log('webserver started on ' + process.pid);

process.on('message',function(msg,socket){
    process.nextTick(function(){
        if(msg == 'c' && socket) {
            socket.readable = socket.writable = true;
            socket.resume();
            server.connections++;
            socket.server = server;         
            server.emit('connection',socket);
            socket.emit('connect');
        }
    })
})

我用curl测了下，新的请求都是新的进程处理，没问题的。