EC2_COMMUNICATING.TF

module "ec2_instance_A" {
  source  = "terraform-aws-modules/ec2-instance/aws"
  version = "~> 3.0"

  name = "ec2_instance_A"

  ami                    = "ami-ebd02392"
  instance_type          = "t2.micro"
  key_name               = "user1"
  monitoring             = true
  vpc_security_group_ids = [module.ec2_instance_A_sg.id]
  subnet_id              = "subnet-eddcdzz4"

  tags = {
    Terraform   = "true"
    Environment = "dev"
  }
}

module "ec2_instance_B" {
  source  = "terraform-aws-modules/ec2-instance/aws"
  version = "~> 3.0"

  name = "ec2_instance_B"

  ami                    = "ami-ebd02392"
  instance_type          = "t2.micro"
  key_name               = "user1"
  monitoring             = true
  vpc_security_group_ids = [module.ec2_instance_B_sg.id]
  subnet_id              = "subnet-eddcdzz4"

  tags = {
    Terraform   = "true"
    Environment = "dev"
  }
}

module "ec2_instance_A_sg" {
  source = "terraform-aws-modules/security-group/aws"

  name        = "ec2_instance_A_sg"
  description = "Security group for web-server with HTTP ports open within VPC"
  vpc_id      = "vpc-12345678"
    
  security_group_id = module.ec2_instance_A_sg.id
  ingress_with_source_security_group_id = [
    {
      description              = "http from service two"
      rule                     = "http-80-tcp"
      source_security_group_id = module.ec2_instance_B_sg.id
    },
  ]
}

module "ec2_instance_B_sg" {
  source = "terraform-aws-modules/security-group/aws"

  name        = "ec2_instance_B_sg"
  description = "Security group for web-server with HTTP ports open within VPC"
  vpc_id      = "vpc-12345678"
  
  security_group_id = module.ec2_instance_B_sg.id
  ingress_with_source_security_group_id = [
    {
      description              = "http from service one"
      rule                     = "http-80-tcp"
      source_security_group_id = module.ec2_instance_A_sg.id
    },
  ]
}