要从位于相同子网的AWS ECS容器实例连接到RabbitMQ EC2实例，您需要确保以下几点：

1. 子网配置：确保ECS和RabbitMQ EC2实例都位于相同的子网中。这将确保它们可以通过私有IP地址相互通信。

2. 安全组配置：确保ECS容器实例的安全组允许出站流量，并且RabbitMQ EC2实例的安全组允许入站流量。这将允许它们互相通信。

下面是一个示例的Terraform代码，演示了如何配置ECS容器实例和RabbitMQ EC2实例的安全组以实现它们之间的通信：

# 创建VPC
resource "aws_vpc" "example" {
  cidr_block = "10.0.0.0/16"
}

# 创建子网
resource "aws_subnet" "example" {
  vpc_id            = aws_vpc.example.id
  cidr_block        = "10.0.0.0/24"
  availability_zone = "us-east-1a"
}

# 创建ECS容器实例安全组
resource "aws_security_group" "ecs_sg" {
  name        = "ecs-sg"
  description = "Allow outbound traffic"
  vpc_id      = aws_vpc.example.id

  egress {
    from_port   = 0
    to_port     = 0
    protocol    = "-1"
    cidr_blocks = ["0.0.0.0/0"]
  }
}

# 创建RabbitMQ EC2实例安全组
resource "aws_security_group" "rabbitmq_sg" {
  name        = "rabbitmq-sg"
  description = "Allow inbound traffic from ECS instances"
  vpc_id      = aws_vpc.example.id

  ingress {
    from_port   = 5672
    to_port     = 5672
    protocol    = "tcp"
    security_groups = [aws_security_group.ecs_sg.id]
  }
}

# 创建ECS容器实例
resource "aws_instance" "ecs_instance" {
  ami           = "ami-0c94855ba95c71c99"
  instance_type = "t2.micro"
  subnet_id     = aws_subnet.example.id
  vpc_security_group_ids = [aws_security_group.ecs_sg.id]
}

# 创建RabbitMQ EC2实例
resource "aws_instance" "rabbitmq_instance" {
  ami           = "ami-0c94855ba95c71c99"
  instance_type = "t2.micro"
  subnet_id     = aws_subnet.example.id
  vpc_security_group_ids = [aws_security_group.rabbitmq_sg.id]
}

在上述代码中，ecs_sg安全组配置允许出站流量，rabbitmq_sg安全组配置允许入站流量，并且只允许来自ecs_sg安全组的流量通过5672端口（RabbitMQ默认端口）进入RabbitMQ EC2实例。

确保您的ECS容器实例和RabbitMQ EC2实例在相同的子网中，并且使用类似的安全组配置，即可实现它们之间的通信。