iOS websocket without handshake - ios

Question

I want to establish a simple local Socket communication on iOS. After looking into other libraries, I found the websocket lib that is now native to Swift since last year works quite well, but comes with a nasty handshake that I would like to disable (otherwise I would have to adjust the server response etc.). My code looks like this:
let webSocketDelegate = WebSocket()
let session = URLSession(configuration: .default, delegate: webSocketDelegate, delegateQueue: OperationQueue())
let url = URL(string: "ws://192.168.43.1:6000")!
let webSocketTask = session.webSocketTask(with: url)
func send() {
DispatchQueue.global().asyncAfter(deadline: .now() + 1) {
send()
webSocketTask.send(.string("New Message")) { error in
if let error = error {
print("Error when sending a message \(error)")
}
}
}
}
webSocketTask.receive { result in
switch result {
case .success(let message):
switch message {
case .data(let data):
print("Data received \(data)")
case .string(let text):
print("Text received \(text)")
}
case .failure(let error):
print("Error when receiving \(error)")
}
}
webSocketTask.resume()
I googled and found nw_ws_options_set_skip_handshake, but I could not find an example how to use it. Any ideas?

Answer 1

As #SteffenUllrich suggested, I looked more into TCP socket communication and found a simple way to communicate. Here my solution, hope it will help someone else:
let queue = DispatchQueue(label: "TCP Client Queue")
let connection = NWConnection(to: NWEndpoint.hostPort(host: "192.168.99.1", port: 7000), using: NWParameters.init(tls: nil))
func connect() {
connection.stateUpdateHandler = { (newState) in
switch (newState) {
case .ready:
print("Socket: ready")
sendString(text: "Hello server!")
receiveMsg()
default: print("Socket: \(newState)")
}
}
connection.start(queue: queue)
}
func receiveMsg() {
connection.receive(minimumIncompleteLength: 1, maximumLength: 1000, completion: { (data, context, isComplete, error) in
if((data) != nil){
let text:String = String(decoding: data!, as: UTF8.self)
//send string to handler function, trim linebreak for single line commands
handleMsg(msg: text.trimmingCharacters(in: .newlines))
}
else{receiveMsg()//go back to receiving}
})
}
func receiveFile() {
print("Receiving file...")
//fileSize was sent before submission
connection.receive(minimumIncompleteLength: Int(fileSize), maximumLength: Int(fileSize)+1000, completion: { (data, context, isComplete, error) in
saveFile(data: data!)//save data to file
})
}
func sendString(text:String) {
let data:Data? = "\(text)\n".data(using: .utf8)//add linebreak to single line string, otherwise it does not release transmission
connection.send(content: data, completion: NWConnection.SendCompletion.contentProcessed(({ (NWError) in
if (NWError == nil) {
print("Data was sent to TCP destination ")
} else {
print("ERROR! Error when data (Type: Data) sending. NWError: \n \(NWError!)")
}
})))
}
You just need to call connect() to start the connection, use sendString() to send some text. Receiving should run constantly. I didn't share the command handler, but it re-runs receiveMsg() on a regular command, and receiveFile() when a file transmission is initiated by the server (the init also contains the fileSize required to set the expected bytesize in the receive() function!).