function main() {
    var depths = [];
    while (true) {
        for (var i = 0; i < exchanges.length; i++) {
            if (depths[i] == null) {
                // 创建异步操作
                depths[i] = exchanges[i].Go("GetDepth");
            }
        }
        var failed = 0;
        for (var i = 0; i < exchanges.length; i++) {
            if (typeof(depths[i].wait) != "undefined") {