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The Sandbox provides some basic network tools. You can run web services and expose them to the internet behind SSL-terminated endpoints. This is useful for web development, API testing, and running interactive applications with LLMs (think v0, reflex.build, etc).

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Exposing Ports

You can expose ports from your Sandbox in two ways: statically at creation time, or dynamically at runtime.

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Static Port Exposure

Specify ports when creating the sandbox to have them exposed immediately with public URLs: 
from beam import Sandbox, Image, PythonVersion

# Create a sandbox with pre-exposed ports
sandbox = Sandbox(
    image=Image(python_version=PythonVersion.Python311),
    ports=[8000, 8080, 3000]  # Ports exposed at creation
)

sb = sandbox.create()

# URLs are immediately available
urls = sb.list_urls()
for port, url in urls.items():
    print(f"Port {port} exposed at: {url}")

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Dynamic Port Exposure

You can also expose ports dynamically after the sandbox is created using the expose_port() method.

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Expose a port

from beam import Sandbox, Image, PythonVersion

sandbox = Sandbox(image=Image(python_version=PythonVersion.Python311))
sb = sandbox.create()

# Expose port 8000
url = sb.expose_port(8000)
print(f"Port 8000 exposed at: {url}")

# The URL will be something like:
# https://384ced3c-f837-4429-bada-39e0b965c9f4-8000.app.beam.cloud

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Expose multiple ports

# Expose multiple ports
ports = [8000, 8080, 3000]
urls = {}

for port in ports:
    url = sb.expose_port(port)
    urls[port] = url
    print(f"Port {port} exposed at: {url}")

# Access different services
print(f"Main app: {urls[8000]}")
print(f"Admin panel: {urls[8080]}")
print(f"API server: {urls[3000]}")

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List exposed ports/preview URLs

# List exposed ports & preview URLs
urls = sb.list_urls()
for port, url in urls.items():
    print(f"Port {port} exposed at: {url}")

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Network Security

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Blocking Outbound Traffic

You can block all outbound network access from your Sandbox while still allowing inbound connections to exposed ports. This is useful for security-sensitive workloads or when executing untrusted code. 
from beam import Sandbox, Image, PythonVersion

# Create a sandbox with blocked outbound network
sandbox = Sandbox(
    image=Image(python_version=PythonVersion.Python311),
    block_network=True,  # Block all outbound traffic
)

sb = sandbox.create()

# The sandbox can still receive requests on exposed ports
url = sb.expose_port(8000)
print(f"Port 8000 exposed at: {url}")

# But it cannot make outbound connections to external services
With block_network=True, the Sandbox can receive requests on exposed ports but cannot initiate outbound connections to external services.

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Allow Lists (CIDR Ranges)

For more fine-grained control, you can specify an allow list of CIDR ranges that your Sandbox is permitted to connect to. All other outbound traffic will be blocked. 
from beam import Sandbox, Image, PythonVersion

# Create a sandbox with an allow list
sandbox = Sandbox(
    image=Image(python_version=PythonVersion.Python311),
    allow_list=[
        "8.8.8.8/32",      # Allow Google DNS
        "10.0.0.0/8",      # Allow private network range
        "2001:db8::/32",   # Allow IPv6 range
    ],
)

sb = sandbox.create()

# The sandbox can only connect to addresses in the allow list
# All other outbound traffic is blocked
Important Notes:
  • Maximum of 10 CIDR entries per Sandbox
  • Supports both IPv4 and IPv6 addresses
  • Must use proper CIDR notation (e.g., "8.8.8.8/32" for a single IP, "10.0.0.0/8" for a range)
  • Cannot use allow_list and block_network together - they are mutually exclusive
  • Invalid CIDR values will trigger an error at creation time

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Updating Network Permissions at Runtime

You can dynamically update the network permissions of a running Sandbox without restarting it. This allows you to change access policies during the sandbox’s lifetime. 
from beam import Sandbox, Image, PythonVersion

# Create a sandbox with no network restrictions
sandbox = Sandbox(image=Image(python_version=PythonVersion.Python311))
sb = sandbox.create()

# Later, block all outbound traffic
sb.update_network_permissions(block_network=True)

# Or update to use an allowlist instead
sb.update_network_permissions(
    allow_list=[
        "8.8.8.8/32",      # Allow Google DNS
        "10.0.0.0/8",      # Allow private network range
    ]
)

# Remove all restrictions
sb.update_network_permissions(block_network=False, allow_list=[])
Important Notes:
  • Cannot use block_network=True and allow_list together - they are mutually exclusive
  • Exposed ports remain accessible regardless of network restrictions
  • Changes take effect immediately without requiring a restart