SwiftNIO: TCP Server not sending data back - swift-nio

Question

I have written my own handler for SwiftNIO but I cannot get it to send anything.
class MyHandler: ChannelInboundHandler
{
public typealias InboundIn = ByteBuffer
public typealias OutboundOut = ByteBuffer
public func channelRead(context: ChannelHandlerContext, data: NIOAny)
{
let message = "The weather is sunny.\n"
let length = message.utf8.count
var buffer = context.channel.allocator.buffer(capacity: length)
buffer.writeString(message)
let out = self.wrapOutboundOut(buffer)
context.write(out, promise: nil)
}
public func channelReadComplete(context: ChannelHandlerContext)
{
context.flush()
}
public func errorCaught(context: ChannelHandlerContext, error: Error)
{
print("error: ", error)
context.close(promise: nil)
}
}
If I just leave the channelRead function as below it successfully echoes the incoming text:
public func channelRead(context: ChannelHandlerContext, data: NIOAny)
{
context.write(data, promise: nil)
}
What am I doing wrong?

Answer 1

You're not doing anything wrong, this should work just fine. It'll send back The weather is sunny.\n every time any data is received.
I also tried it and it works:
$ nc localhost 9999
How's the weather?
The weather is sunny.
How are you?
The weather is sunny.
The complete code I used was
import NIO
class MyHandler: ChannelInboundHandler
{
public typealias InboundIn = ByteBuffer
public typealias OutboundOut = ByteBuffer
public func channelRead(context: ChannelHandlerContext, data: NIOAny)
{
let message = "The weather is sunny.\n"
let length = message.utf8.count
var buffer = context.channel.allocator.buffer(capacity: length)
buffer.writeString(message)
let out = self.wrapOutboundOut(buffer)
context.write(out, promise: nil)
}
public func channelReadComplete(context: ChannelHandlerContext)
{
context.flush()
}
public func errorCaught(context: ChannelHandlerContext, error: Error)
{
print("error: ", error)
context.close(promise: nil)
}
}
let group = MultiThreadedEventLoopGroup(numberOfThreads: System.coreCount)
defer {
try! group.syncShutdownGracefully()
}
let bootstrap = ServerBootstrap(group: group)
.serverChannelOption(ChannelOptions.socketOption(.so_reuseaddr), value: 1)
.childChannelInitializer { channel in
channel.pipeline.addHandler(MyHandler())
}
let serverChannel = try bootstrap.bind(host: "localhost", port: 9999).wait()
try serverChannel.closeFuture.wait()