在 NS2 中模拟无线传感器网络的路由协议时，从函数内部访问节点会出现错误 "No such variable"

Question

我正在尝试为 60 个节点和 1 个移动接收器编写代码，其中 18 个节点充当高层节点或 Backbone 个节点。移动sink周期性更新位置，仅Backbone个节点，其他节点可在需要时查询sink位置。

#node creation
#Node 1 to 18 are backbone nodes
#nodes 19 to 59 are normal sensor nodes
#node 60 is the mobile sink
    set node_(0) [$ns node]
    set node_(1) [$ns node]
    .
    .
    .
#node no 60 is the mobile sink..
    set node_(60) [$ns node]

    
    #node X Y coordinate initialized
    $node_(0) set X_ 2
    $node_(0) set Y_ 3
    $node_(1) set X_ 517
    $node_(1) set Y_ 299
    .
    .
    $node_(63) set  X_ 306
    $node_(63) set  Y_ 178
    
    proc distBN {n1 n2 nid1 nid2} {
        set x1 [expr int([$n1 set X_])]
        set y1 [expr int([$n1 set Y_])]
        set x2 [expr int([$n2 set X_])]
        set y2 [expr int([$n2 set Y_])]
        set d [expr int(sqrt(pow(($x2-$x1),2)+pow(($y2-$y1),2)))]
        #checking that it is in the transmission range i.e 100m
        if {$d<100} {
            if {$nid2!=$nid1} {
                return $d;
            }            
        }
    }
    
    
    #This function starts the transmission of Mobile Sink location every 5 seconds 
    proc locTrans {} {
        global ns
        set dist_min 101
        set dist 101
        set sink_loc 60
        puts "[$ns now] : Finding the nearest backbone node to sink node $sink_loc..."
        for {set j 0} {$j < 19} {incr j} {
            set dist [expr "distBN $node_($sink_loc) $node_($j) $sink_loc $j"]; ## <<< THIS LINE
            puts "Distance between sink and node $j is $dist...\n"
            if{$dist_min > $dist} {
                set dist_min $dist 
            }
            puts "Running loop for $j time...\n"
        }
        puts "The smallest distance is $dist_min between node_(60) and node_($j)\n"
        puts "[$ns now] : transmitting sink location to nearest backbone node...\n"
        $ns at [expr [$ns now] + 3.0] "locTrans"  
    }

过程 locTrans() 调用另一个函数 distBN() 来计算传入参数的节点之间的距离。但是运行代码给出了以下错误：

> ns: locTrans: can't read "node_(60)": no such variable
    while executing
"expr "distBN $node_($sink_loc) $node_($j) $sink_loc $j""
    (procedure "locTrans" line 9)
    invoked from within
"locTrans"

Error screenshot

Answer 1

问题是全局 node_ 数组不在过程内的范围内（因为 Tcl 仅在您明确要求时才使 non-local 变量可用）。幸运的是，修复很简单：将上面几行的 global ns 命令更新为：

global ns node_

还要注意您的代码中有几个错误：您没有处理正确测量节点到自身距离的情况（现在，您实际上返回的是空字符串；我打赌你不想要那个！）并且你已经将对 distBN 的调用写错了，应该这样做：

set dist [distBN $node_($sink_loc) $node_($j) $sink_loc $j]

你写的是...行不通。

在 NS2 中模拟无线传感器网络的路由协议时，从函数内部访问节点会出现错误 "No such variable"

While simulating a routing protocol for Wireless Sensor Network in NS2, accessing the nodes from inside the a function gives error "No such variable"

function

routes

tcl

ns2