protobuf-udp-chat

README

Chat Using Protocol Buffers Via UDP

This prototype uses Protocol Buffer. It is mainly the same prototype as protobuf-tcp-chat, but using UDP instead of TCP.

Before we see some details, let's do go build and run it in three terminals as follows:

./protobuf-udp-chat alice 127.0.0.1 12340

./protobuf-udp-chat bob 127.0.0.1 12341

./protobuf-udp-chat charly 127.0.0.1 12342

Write your message and send it by the return key.

Ctrl-C quits the chat.

UDP Instead Of TCP

We use protocol "udp" instead of "tcp" in the net package functions.

publishingListener, err := net.ListenPacket("udp", publishingService)
conn, err := net.Dial("udp", publishingService)

displayingListener, err := net.ListenPacket("udp", displayingService)
conn, err := net.Dial("udp", recipient)

We take care of the buffer size according to RFC 791.

// The maximum safe UDP payload is 508 bytes.
// This is a packet size of 576 (IPv4 minimum reassembly buffer size),
// minus the maximum 60-byte Ip header and the 8-byte UDP header.
bufferSize = 508

Features

• informs about joining and leaving members
• writes a log file
• set of internal commands, to which you can add new commands quickly.

Message Types

It uses an enumeration in the message to appropriately handle the types regarding request and reply.

message Member {
    string name = 1;
    string ip = 2;
    string port = 3;
    bool leader = 4;
}

message MemberList {
    repeated Member member = 1;
}

// Services are mapped by request/reply message types
message Message {
    enum MessageType {
        // messages to handle subscriptions at the publishing service
        SUBSCRIBE_REQUEST = 0;
        SUBSCRIBE_REPLY = 1;

        // messages to handle unsubscriptions at the publishing service
        UNSUBSCRIBE_REQUEST = 2;
        UNSUBSCRIBE_REPLY = 3;

        // messages to publish chat messages via the publishing service
        PUBLISH_REQUEST = 4;
        PUBLISH_REPLY = 5;
    }
    MessageType msgType = 1;
    Member  sender = 2;
    string  text = 3;
    MemberList memberList = 4;
}

The first client starts the service running under a well-known address, and its property 'Member.leader' is true. The service handles all messages and subscriptions.

Internal Commands

• \self shows information of this member

• \list lists all members; only applicable to publishing service

• \publisher shows well-known publisher address

• \logfile shows log file of this member