iOS 中使用 webSocket
是服务器和app之间的一种通信方式
webSocket 实现了服务端推机制（主动向客户端发送消息）。新的 web 浏览器全都支持 WebSocket，这使得它的使用超级简单。通过 WebSocket 能够打开持久连接，大部分网络都能轻松处理 WebSocket 连接。在 iOS 中使用 WebSocket 比较麻烦，你必须进行大量的设置，而且内置的 API 根本帮不上忙。这时 Starscream 出现了——这个小巧、易于使用的库让你所有的烦恼不翼而飞。
Client1 ——-> cloud ————>client2,3,4…
<——-返回ack <——-返回ack
一，基本使用
1根据url创建socket
var request = URLRequest(url: URL(string: "url")!)
request.timeoutInterval = 5//超时时间
socket = WebSocket(request: request)
socket.delegate = self//接收到消息走代理方法
2。发送消息
socket.write(string: sendStr)
3.接收消息，在代理方法中
func websocketDidReceiveMessage(socket: WebSocketClient, text: String) {
//接收到字符串消息
}
func websocketDidReceiveData(socket: WebSocketClient, data: Data) {
printLog(“(data)”)//接收到data消息
}
二 常见问题
1.如何确保client向特定的client发送消息
“(storeID!)-(deviceNumber)-(deviceGlobalID!)”.uppercased() 这些标志客户端的唯一性
发送消息时带着要发送给哪些client（唯一标识性数组）发送给cloud，cloud根据要发送给的client数组向相应的client发送消息
/// 发送一条消息到指定的多个设备
///
/// - Parameters:
/// - deviceID: web socket 登陆名称数组
/// - text: 要发送的文本
func sendTextTo(deviceIDs: [String], text: String) {
if socket == nil {
return
}
if socket.isConnected == false {
return
}
let cmdMessage = AldeloMessage(Type: 1, MsgGID: UUID().uuidString, Receivers: deviceIDs, Content: text, Time: nil, Publisher: nil, axOrderIDs: nil)
if let sendStr = AldeloMessage.toJsonString(messages: [cmdMessage]) {
socket.write(string: sendStr)
}
}
2.如何保持链接
十分钟发送一次心跳包，app进入前台时，app断网重连时，app失去web连接时，重新连接
NotificationCenter.default.addObserver(self, selector: #selector(appDidBecomeActive), name: UIApplication.didBecomeActiveNotification, object: nil)
do {
try reachability.startNotifier()
} catch {
print("Unable to start notifier")
}
reachability.whenReachable = { [weak self] reachability in
self?.reconnectTimes = 10
firstly {
after(seconds: 3)
}.done {
if self?.socket == nil {
return
}
self?.socket.connect()
}
}
if #available(iOS 10.0, *) {
timer = Timer.scheduledTimer(withTimeInterval: 30, repeats: true) { timer in
let now = Date().timeIntervalSince1970
let s = now - self.lastReceivedMessageTime
if s >= 600 && s <= 660 {
self.sendHeartBeat()
} else if s > 660 {
self.reconnect()
}
}
} else {
timer = Timer.scheduledTimer(timeInterval: 30, target: self, selector: #selector(handleTimer), userInfo: nil, repeats: true)
}
@objc func handleTimer(timer: Timer) {
let now = Date().timeIntervalSince1970
let s = now - self.lastReceivedMessageTime
if s >= 600 && s <= 660 {
self.sendHeartBeat()
} else if s > 660 {
self.reconnect()
}
}
@objc func appDidBecomeActive(_ application: UIApplication) {
firstly {
after(seconds: 3)
}.done {
if self.socket == nil {
return
}
if self.socket.isConnected == false && self.reachability.connection != .none {
self.socket.connect()
}
}
}
3.如何保证消息送达
client到cloud：client中维护一个message数据表（包括字段是否发送成功sent）cloud收到消息之后向client返回ack，client收到ack后将该条message标记为sent=1已发送
60秒client未收到ack，视为发送失败，从新发送
cloud端message表中已经存在该条消息，则忽略，但是向客户端client发送ack
cloud到clinet：client收到消息后向cloud返回ack，cloud收到ack标记消息为已发送成功， 60秒cloud未收到ack，视为发送失败，从新发送
client端message表中已经存在该条消息，则忽略，但是向客户端client发送ack
func websocketDidReceiveMessage(socket: WebSocketClient, text: String) {
printLog("Web Socket receive (text)")
lastReceivedMessageTime = Date().timeIntervalSince1970
if text == "$" {
printLog("Received Heart Beat!!!!")
return
}
guard let messageArray = AldeloMessage.from(jsonData: text.data(using: .utf8)!) else { return }
for message in messageArray {
if message.Type == 99 { //ACK
DBPool.write { db in
try? db.execute("Update AldeloMessageRecord Set sent = 1 Where messageGID = '(message.MsgGID)'")
}
continue
}
//收到消息后回复ACK,这样服务器会标记这条消息发送成功
sendACK(message: message)
//从收到的消息列表中对比msgid, 如果已经收到过,则忽略这条消息, 去重处理
var shouldReturn = false
DBQueue.inDatabase { db in
do {
if let count = try Int.fetchOne(db, "Select count(*) from AldeloMessageRecord where messageGID = '(message.MsgGID)'"), count > 0 {
//数据库里有这条消息,说明已经收到过,忽略掉
Log.shareInstance.log(message: "Websocket 收到重复消息,已忽略")
printLog("Websocket 收到重复消息,已忽略")
shouldReturn = true
}
} catch {
Log.shareInstance.log(message: "读取数据库错误")
printLog("读取数据库错误")
self.createTable()
}
}
if shouldReturn == true {
return
}
// if let count = DatabaseOption().intForSql("Select count(*) from AldeloMessageRecord where messageGID = '(message.MsgGID)'"), count > 0 {
// //数据库里有这条消息,说明已经收到过,忽略掉
// Log.shareInstance.log(message: "Websocket 收到重复消息,已忽略")
// printLog("Websocket 收到重复消息,已忽略")
// return
// }
//发完ACK将message存到数据库
let aMessage = AldeloMessageRecord()
aMessage.messageGID = message.MsgGID
aMessage.type = message.Type
aMessage.time = message.Time
aMessage.publisher = message.Publisher
if message.Type == 1 { //text
guard let content = message.Content else { continue }
aMessage.message = message.Content
if content.hasPrefix("cmd::") {
let ar = content.components(separatedBy: "::")
var para: String? = nil
if ar.count == 3 {
para = ar[2]
}
let cmdString = "(ar[0])::(ar[1])".lowercased()
let command = AldeloCommand(rawValue: cmdString) ?? AldeloCommand.unknown
if command == .clinePrint {
if let ar = para?.components(separatedBy: ","), ar.count == 2 {
if let orderID = Int64(ar[0]), orderID > 0 {
gotPrintCommandBlock?([orderID],ar[1].boolValue(),true, message)
delegate?.receivedPrintCommand(axOrderIDs: [orderID], packingPrint: ar[1].boolValue(), isClientWebSocket: true)
}
}
} else {
gotCommandBlock?(command,para, message)
delegate?.receivedCommand(cmd: command,parameter: para, message: message)
}
} else {
gotMessageBlock?(message)
delegate?.receivedMessage(message: message)
}
} else if message.Type == 2 { //print
guard let orderIDs = message.axOrderIDs else { return }
aMessage.message = "(orderIDs)"
gotPrintCommandBlock?(orderIDs,true,false,message)
delegate?.receivedPrintCommand(axOrderIDs: orderIDs, packingPrint: true, isClientWebSocket: false)
} else if message.Type == 3 { //QR payment
guard let content = message.Content else { continue }
aMessage.message = content
gotQRPaymentBlock?(content)
delegate?.receivedQRPayment(content: content)
} else if message.Type == 4 { //cloud 强制反激活
printLog("cloud 强制反激活 .....")
}
DBPool.write { db in
try? aMessage.insert(db)
}
}
}
starscream地址：https://github.com/daltoniam/starscream