ConnVerifier

ConnVerifier is a Go TCP keepalive stress tool used to verify whether long-lived TCP sessions remain stable after passing through NAT.

Components

• server.go — Minimal echo server. It listens on a configurable TCP port, accepts connections, and echoes back every byte it receives.
• client.go — Concurrent connection generator. It maintains many TCP sessions, sends periodic heartbeats, retries with exponential backoff, and prints per-second stats.

Build

go build server.go
go build client.go

Each file has its own main, so they must be built separately.

Usage

1. Start the server:

   ./server -addr :9000

2. Start the client:

   ./client \
     -addr <server-ip>:9000 \
     -clients 10000 \
     -start-rate 500 \
     -heartbeat 30s \
     -dial-timeout 5s \
     -io-timeout 5s \
     -min-backoff 500ms \
     -max-backoff 1m

Client Flags

Flag	Default	Description
-addr	127.0.0.1:9000	Target server address
-clients	1000	Target number of concurrent connections
-start-rate	100	Max new connections started per second
-heartbeat	30s	Heartbeat interval
-dial-timeout	5s	TCP dial timeout
-io-timeout	5s	Deadline for heartbeat write/read
-min-backoff	500ms	Initial reconnect backoff
-max-backoff	1m	Maximum reconnect backoff

Metrics

The client prints one stats line per second:

stats target=1000 active=998 connected=1000 drops=12 heartbeats=42 ack=42 dials=3 reconnects=12

Field	Description
target	Configured target connection count
active	Currently active connections
connected	Total successful dial count since startup
drops	Total connections that dropped and entered reconnect flow
heartbeats	Total heartbeat writes sent
ack	Total heartbeat responses successfully read
dials	Total dial failures
reconnects	Total reconnect attempts scheduled after dropouts

Graceful Shutdown

• server.go listens for SIGINT/SIGTERM, closes the listener, waits for active goroutines, then prints server stopped.
• client.go listens for SIGINT/SIGTERM, prints shutting down..., waits 5 seconds for in-flight cleanup, then exits.

Notes

• Raise ulimit -n before starting the client so the OS allows enough file descriptors.
• No external dependencies — uses only the Go standard library.

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ConnVerifier / 连接稳定性验证工具

ConnVerifier 是一个 Go 版 TCP Keepalive 压测工具，用于验证经过 NAT 之后的 TCP 长连接是否能够稳定维持。

组成部分

• server.go — 最小回声服务，监听可配置端口，接受连接后将收到的字节原样回写。
• client.go — 并发连接器，负责维持大量 TCP 会话、定期发送心跳、指数退避重连，并输出每秒统计信息。

构建

go build server.go
go build client.go

两个文件都包含 main，需要分别编译。

使用方式

1. 启动服务端：

   ./server -addr :9000

2. 启动客户端：

   ./client \
     -addr <server-ip>:9000 \
     -clients 10000 \
     -start-rate 500 \
     -heartbeat 30s \
     -dial-timeout 5s \
     -io-timeout 5s \
     -min-backoff 500ms \
     -max-backoff 1m

客户端参数

参数	默认值	说明
-addr	127.0.0.1:9000	目标服务器地址
-clients	1000	目标并发连接数
-start-rate	100	每秒最大新连接数
-heartbeat	30s	心跳间隔
-dial-timeout	5s	TCP 拨号超时
-io-timeout	5s	心跳读写超时
-min-backoff	500ms	初始重连退避
-max-backoff	1m	最大重连退避

指标说明

客户端每秒输出一行统计信息：

stats target=1000 active=998 connected=1000 drops=12 heartbeats=42 ack=42 dials=3 reconnects=12

字段	说明
target	配置的目标连接数
active	当前活跃连接数
connected	启动以来累计成功拨号数
drops	累计掉线次数
heartbeats	累计心跳发送数
ack	累计心跳确认数
dials	累计拨号失败数
reconnects	累计重连尝试次数

优雅关闭

• server.go 监听 SIGINT/SIGTERM，关闭监听器后等待活跃 goroutine 退出，打印 server stopped。
• client.go 监听 SIGINT/SIGTERM，打印 shutting down...，等待 5 秒收尾后退出。

注意事项

• 运行前请提升 ulimit -n，确保文件描述符数量足够。
• 无外部依赖，仅使用 Go 标准库。