---
name: "tcpconnect.bt.bt"
section: "8"
platform: "linux"
package: "bpftrace"
version: "0.17.0-1"
release: "Debian 12 (Bookworm)"
platforms: ["linux"]
url: "https://new.carta.tech/tcpconnect.bt.bt"
---

# tcpconnect.bt.bt(8)

Trace TCP active connections (connect()). Uses Linux bpftrace/eBPF

## NAME

tcpconnect.bt - Trace TCP active connections (connect()). Uses Linux bpftrace/eBPF

## SYNOPSIS

**tcpconnect.bt**

## DESCRIPTION

This tool traces active TCP connections (eg, via a connect() syscall; accept() are passive connections). This can be useful for general troubleshooting to see what connections are initiated by the local server.

All connection attempts are traced, even if they ultimately fail.

This works by tracing the kernel tcp\_v4\_connect() and tcp\_v6\_connect() functions using dynamic tracing, and will need updating to match any changes to these functions.

Since this uses BPF, only the root user can use this tool.

## REQUIREMENTS

CONFIG\_BPF and bpftrace.

## EXAMPLES

- Trace all active TCP connections:

  \# **tcpconnect.bt**

-

  ## FIELDS

- TIME(s)

  Time of the call, in HH:MM:SS format.

- PID

  Process ID

- COMM

  Process name

- SADDR

  Source IP address.

- SPORT

  Source port.

- DADDR

  Destination IP address.

- DPORT

  Destination port

## OVERHEAD

This traces the kernel tcp\_v\[46\]\_connect functions and prints output for each event. As the rate of this is generally expected to be low (\< 1000/s), the overhead is also expected to be negligible. If you have an application that is calling a high rate of connects()s, such as a proxy server, then test and understand this overhead before use.

## SOURCE

This is from bpftrace

-

  https://github.com/iovisor/bpftrace

Also look in the bpftrace distribution for a companion \_examples.txt file containing example usage, output, and commentary for this tool.

This is a bpftrace version of the bcc tool of the same name. The bcc tool may provide more options and customizations.

-

  https://github.com/iovisor/bcc

## OS

Linux

## STABILITY

Unstable - in development.

## AUTHOR

Brendan Gregg, adapted for bpftrace by Dale Hamel

## SEE ALSO

[tcpaccept.bt(8)](/tcpaccept.bt/8.md), [funccount(8)](/funccount/8.md), [tcpdump(8)](/tcpdump/8.md)