即时消息传递-Java上的单连接或多线程

Question

I'm supposed to send out instant emails to a set of contacts in a time-critical application.

Say, I have n contacts in the list. So, i can do either one of the following:

i.) send out a single email to all of these n contacts as multiple receivers.

ii.)send n emails, separately one for each receiver, in n threads.

In the first case, i'm setting up a single connection at my end and just sending it out.

In the second, n connections to my smtp server. However, it is concurrent.

Which one is faster?

Answer 1

第一种情况比较快，因为它只向服务器发送大约x个字节（消息的大小），第二种情况是通过（我假设）单根导线（无论字节是否交错）向服务器发送大约x * n个字节。

Answer 2

With your first option only one copy will be sent to every recipient and it should be comparatively faster. But depends the amount of recipient and server capacity for it. With your second option though its concurrent 'n' connections are made and same copies will be sent in each thread. Ratio :: A Thread run = A mail sent to individual recipient.

Yeas, second option will be better if you have to schedule task for sending mails to larger masses. for ex: A MNC sending mails to its 80000 Employees in that case Recipient limit may come handy and mails would be sent in chunk of X' recipient ie 5000 employee at once. Whereas in this case first option may turn into failure because of server failure.

Practical Example: I work in Infotech and here group of mail recipients are maintained depending upon department but there is one general group where mail id of all recipient are stored. By mistake one of the user triggered mail to that general group and after that session of mails began causing complete server failure.

In this case factor like server capacity has larger impact.

Answer 3

email are not designed to be instant messaging.
If you want instant messaging you need p2p type of connection. If you intend to use emails than it does not matter how you will send them, too many other factors will interfere. Generally 1st method will be (marginally) faster as it will allow mail server to optimise the way the messages are sent.

See ServerSocket() http://docs.oracle.com/javase/7/docs/api/java/net/ServerSocket.html and Socket() docs.oracle.com/javase/7/docs/api/java/net/Socket.html

Again you will need p2p as above if you need guaranteed delivery, if speed is more important and the server/client are on the same network you may want to look at MulticastSocket http://download.java.net/jdk7/archive/b123/docs/api/java/net/ …