I'm attempting to use NWConnection as a websocket given a NWEndpoint returned by NWBrowser, setup like: let tcpOptions = NWProtocolTCP.Options() tcpOptions.enableKeepalive = true tcpOptions.keepaliveIdle = 2 let parameters = NWParameters(tls: nil, tcp: tcpOptions) parameters.allowLocalEndpointReuse = true parameters.includePeerToPeer = true let options = NWProtocolWebSocket.Options() options.autoReplyPing = true options.skipHandshake = true parameters.defaultProtocolStack.applicationProtocols.insert(options, at: 0) self.connection = NWConnection(to: endpoint, using: parameters) The initial connection does make it to the ready state but when I first try to send a text message over the websocket, i get nw_read_request_report [C1] Receive failed with error "Input/output error" nw_flow_prepare_output_frames Failing the write requests [5: Input/output error] nw_write_request_report [C1] Send failed with error "Input/output error" immediately, and the websocket is closed. Send code here: let encoder = JSONEncoder() let dataMessage = try encoder.encode(myMessage) let messageMetadata = NWProtocolWebSocket.Metadata(opcode: .text) let context = NWConnection.ContentContext(identifier: "send", metadata: [messageMetadata]) connection.send(content: dataMessage, contentContext: context, completion: .contentProcessed({ error in if let error = error { print (error) } })) What would typically cause the Input/output error when writing? Am I doing something obviously wrong or is there something else I can do to get additional debug information? Thanks in advance for any help.