digraph G
{
    rankdir = LR

    node
    [
        fontname    = "Inconsolata"
        fontsize    = 22
        shape       = record
        style       = rounded
    ]

    edge
    [
        fontname    = "Inconsolata"
        fontsize    = 20
        arrowhead   = vee
        arrowtail   = vee
    ]

    "user\nagents"  -> "web\nserver"    [label="HTTP",dir=both]
    "web\nserver"   -> "your\napp"      [label="PSGI",dir=both,fontcolor=blue,fontsize=30]

    "web\nserver" [style="rounded,filled",fillcolor="#FFFF88"]
}