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server.go
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server.go
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package main
import (
"fmt"
"log"
"net"
)
// TODO: normalize format for sending messages to cchat, json?
const Bufsize int = 256
// enum for types of messages
type MessageType int
const (
NewConnection MessageType = iota
Disconnect MessageType = iota
Send MessageType = iota
)
// Message contains information about communication between the server and a client
// or a client broadcasting a message to other clients
type Message struct {
Type MessageType
Sender Client
Text string
}
// Client is a representation of someone connected to the server
type Client struct {
Buffer []byte
Username string // Not unique, TODO: make usernames unique (would also have to change DB)
Conn net.Conn
}
// Server contains information about all connected clients as well as
// means of logging and accepting new connections
type Server struct {
Clients map[string]*Client
Messages chan Message
Listener net.Listener
DB *GochatDB
}
// Connect handles initial connection for newly registered client, if
// establishment of connection fails, close the connection and ignore it
func Connect(conn net.Conn, server Server) {
client := Client{
Buffer: make([]byte, Bufsize),
Conn: conn,
}
_, err := client.Conn.Write([]byte("SERVER_INFO: Welcome to go-chat! Please enter a username: "))
if err != nil {
log.Printf("Could not write to: %s\n", conn.RemoteAddr())
conn.Close()
return
}
n, err := conn.Read(client.Buffer)
if err != nil {
log.Printf("Could not read username from: %s\n", conn.RemoteAddr())
conn.Close()
return
}
client.Username = string(client.Buffer[0 : n-1])
// Notify other clients of new connection
server.Messages <- Message{
Type: NewConnection,
Sender: client,
}
// Start event loop for client
go client.Run(server)
}
// Run handles event loop for one client and is meant to be used as a goroutine
func (client Client) Run(server Server) {
for {
n, err := client.Conn.Read(client.Buffer)
if err != nil {
server.Messages <- Message{
Type: Disconnect,
Sender: client,
}
return
}
server.Messages <- Message{
Type: Send,
Sender: client,
Text: string(client.Buffer[0 : n-1]),
}
}
}
// Start starts up an empty server based on some configuration,
// errors if unable to listen to port given in the config
func Start(conf GochatConfig, db *GochatDB) (*Server, error) {
server := &Server{
Clients: map[string]*Client{},
Messages: make(chan Message),
DB: db,
}
// Start listening for tcp connections at `Conf.Port`
listener, err := net.Listen("tcp", ":"+conf.Port)
if err != nil {
return nil, err
}
server.Listener = listener
return server, nil
}
// Accept is the event loop for accepting new connections onto the server.
// If accepting new connection fails ignore and continue
func (server Server) Accept() {
for {
conn, err := server.Listener.Accept()
if err != nil {
log.Printf("Could not accept connection from %s: %s\n", conn, err)
continue
}
go Connect(conn, server)
}
}
// Run first starts goroutine for accepting new clients onto the server then
// handles event loop for the server managing forwarding of messages to clients
func (server Server) Run() {
go server.Accept()
for {
message := <-server.Messages
switch message.Type {
// New client connected
case NewConnection:
server.Clients[message.Sender.Conn.RemoteAddr().String()] = &message.Sender
outstr := fmt.Sprintf("CONNECT: New user joined with username '%s'\n", message.Sender.Username)
log.Printf(outstr)
for _, client := range server.Clients {
if client.Conn.RemoteAddr().String() != message.Sender.Conn.RemoteAddr().String() {
go client.Conn.Write([]byte(outstr))
}
}
err := server.DB.LogConnection(message)
if err != nil {
log.Printf("Could not log new connection database: %s\n", err)
}
// Client has disconnected
case Disconnect:
message.Sender.Conn.Close()
delete(server.Clients, message.Sender.Conn.RemoteAddr().String())
outstr := fmt.Sprintf("DISCONNECT: User '%s@%s' has disconnected\n", message.Sender.Username, message.Sender.Conn.RemoteAddr())
log.Printf(outstr)
for _, client := range server.Clients {
if client.Conn.RemoteAddr().String() != message.Sender.Conn.RemoteAddr().String() {
go client.Conn.Write([]byte(outstr))
}
}
// Client has sent a message
case Send:
outstr := fmt.Sprintf("SEND: %s: %s\n", message.Sender.Username, message.Text)
log.Printf(outstr)
for _, client := range server.Clients {
if client.Conn.RemoteAddr().String() != message.Sender.Conn.RemoteAddr().String() {
go client.Conn.Write([]byte(outstr))
}
}
err := server.DB.LogMessage(message)
if err != nil {
log.Printf("Could not log message to database: %s\n", err)
}
}
}
}