This is an example of a raw network stream AWS Lambda handler.
Unfortunately, how to set this up to be useful within AWS is the current challenge - there are no direct triggers for accepting a payload from a socket to pass to the AWS Lambda and respond back. AWS Kinesis somewhat supports reading a stream, but doesn't appear to support the response portion. AWS ELB only works with EC2 instances. An SNS queue requires more setup to handle the response back to a TCP response.
The AWS API Gateway is one approach, but only if the payload is always JSON, the gateway will reject non-JSON payloads.
source: http://docs.aws.amazon.com/lambda/latest/dg/use-cases.html
Only potential idea left is to create a small ec2 instance and evaluate socket-activation technique to Invoke the AWS lambda via socket-activation code (then you can use ELB in front of the EC2).