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SDKs connect over TCP and stream binary batches. This is the fastest ingestion path — 64M events/sec — and the default for all native SDKs (Go, Swift, Flutter, C++). 
[[sources.tcp]]
port = 50000
That’s it. The defaults handle most deployments. SDKs authenticate with an API key embedded in each batch.

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Forwarding mode

You can run multiple TCP sources. A common pattern is one port for direct SDK traffic and another for Tell-to-Tell forwarding between regions: 
[[sources.tcp]]
port = 50000

[[sources.tcp]]
port = 8081
forwarding_mode = true
With forwarding_mode = true, the source trusts the original client IP embedded in forwarded batches instead of using the forwarder’s connection IP.

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Backpressure

If the pipeline can’t keep up, batches are dropped rather than blocking. This keeps all connections responsive — no single slow sink stalls ingestion.

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Advanced

Full config reference with defaults: 
[[sources.tcp]]
port = 50000
address = "::"              # Bind address (default: dual-stack IPv4+IPv6)
forwarding_mode = false      # Trust source_ip from upstream forwarders
no_delay = true              # Disable Nagle's algorithm for lower latency
keepalive = true             # TCP keepalive probes
flush_interval = "100ms"     # Flush partial batches after this interval
batch_size = 500             # Messages per batch before flush
max_connections = 10000      # Reject new connections above this limit
buffer_size = 1048576        # Read buffer per connection (1 MB)
socket_buffer_size = 262144  # OS socket buffer (256 KB)
connection_timeout = "0s"    # Idle timeout (0 = no timeout)