How can two elements be connected vertically in both directions(not a slash)？

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A rendering of the current situation:

Code:

flowchart TB
    req1(接收请求)-->state1(验证登录状态)-->logic1(业务逻辑)-->log1(日志显示耗时)-->res1(响应);
    req2(接收请求)-->state2(验证登录状态)-->logic2(业务逻辑)-->log2(日志显示耗时)-->res2(响应);
    req3(接收请求)-->state3(验证登录状态)-->logic3(业务逻辑)-->log3(日志显示耗时)-->res3(响应);
    reqn(接收请求)-->staten(验证登录状态)-->logicn(业务逻辑)-->logn(日志显示耗时)-->resn(响应);

    state1-.-state2-.-state3-.-staten;

    log1-.-log2-.-log3-.-logn;

    style state1 fill:#bbf,stroke:#f66,stroke-width:2px,color:#fff,stroke-dasharray: 5 5;
    style state2 fill:#bbf,stroke:#f66,stroke-width:2px,color:#fff,stroke-dasharray: 5 5;
    style state3 fill:#bbf,stroke:#f66,stroke-width:2px,color:#fff,stroke-dasharray: 5 5;
    style staten fill:#bbf,stroke:#f66,stroke-width:2px,color:#fff,stroke-dasharray: 5 5;
    
    style log1 fill:#bbf,stroke:#f66,stroke-width:2px,color:#fff,stroke-dasharray: 5 5;
    style log2 fill:#bbf,stroke:#f66,stroke-width:2px,color:#fff,stroke-dasharray: 5 5;
    style log3 fill:#bbf,stroke:#f66,stroke-width:2px,color:#fff,stroke-dasharray: 5 5;
    style logn fill:#bbf,stroke:#f66,stroke-width:2px,color:#fff,stroke-dasharray: 5 5;

Hope to show the effect:

There is no veteran player guidance, thank you very much!