Socket.io广播代码报错修复请求：TypeError与SyntaxError问题

报错场景1 #

执行客户端代码：

socket.emit("broadcasting", {
    cmd: "new"
});

报错信息：

0|server | TypeError: Cannot set property 'id' of undefined

报错场景2 #

执行客户端代码：

socket.emit("broadcasting", {
    cmd: "send"
});

报错信息：

0|server | SyntaxError: Unexpected token u in JSON at position 0

对应服务端处理代码 #

socket.on("broadcasting", (data) => {
    if (typeof data != "object") {
        return;
    }

    if(UserInfo[socket.id]){
        if (data.cmd == "new") {
            if (UserInfo[socket.id].rep >= SiteSetting["miclikes"]) {
                io.to(UserInfo[socket.id].idroom).emit("broadcasting", { cmd: "new", it: data.it, user:socket.id });
                socket.emit("broadcasting", { cmd: "new", it: data.it });
                PeerRoom[UserInfo[socket.id].idroom][data.it].id = socket.id;
                PeerRoom[UserInfo[socket.id].idroom][data.it].ev = true;
            } else {
                socket.emit("msg", {
                    cmd: "not",
                    data: {
                        topic: "",
                        force: 1,
                        msg: SiteSetting["miclikes"] + " " + "عدد الايكات المطلوبة للمايك",
                        user: "",
                    },
                });
            }
        } else if (data.cmd == "send") {
            const myfr = JSON.parse(data.mj);
            if (myfr.type == "new-ice-candidate") {
                socket.to(myfr["target"]).emit("broadcasting", {
                    cmd: "send",
                    msgString: JSON.stringify({
                        type: myfr["type"],
                        it: myfr["it"],
                        target: myfr["target"],
                        user: socket.id,
                        candidate: myfr["candidate"],
                    }),
                });
            } else if (myfr.type == "video-offer") {
                socket.to(myfr["target"]).broadcast.emit("broadcasting", {
                    cmd: "send",
                    msgString: JSON.stringify({
                        type: myfr["type"],
                        it: myfr["it"],
                        target: myfr["target"],
                        sdp: myfr["sdp"],
                        user: socket.id,
                    }),
                });
            } else if (myfr["type"] == "hang-up") {
                // if(myfr["target"] == socket.id || VerRoomsOwner(UserInfo[socket.id].power)){
                    if( PeerRoom[UserInfo[socket.id].idroom][myfr["it"]]){
                PeerRoom[UserInfo[socket.id].idroom][myfr["it"]].id = "";
                PeerRoom[UserInfo[socket.id].idroom][myfr["it"]].ev = false;
                io.to(UserInfo[socket.id].idroom).emit("broadcasting", { cmd: "send", msgString: data.mj });
                };
            } else if (myfr["type"] == "video-answer") {
                socket.to(myfr["target"]).emit("broadcasting", {
                    cmd: "send",
                    msgString: JSON.stringify({
                        type: myfr["type"],
                        it: myfr["it"],
                        target: myfr["target"],
                        sdp: myfr["sdp"],
                        user: socket.id,
                    }),
                });
            } else {
                io.to(UserInfo[socket.id].idroom).emit("broadcasting", { cmd: "send", msgString: data.mj });
            }
        }
    }
});

错误原因及修复方案 #

报错1原因与修复 #

• 原因：客户端发送new命令时未携带it字段，导致data.it为undefined，进而PeerRoom[UserInfo[socket.id].idroom][data.it]指向undefined，无法设置id属性；同时未校验PeerRoom中房间和对应it项是否存在。
• 修复：增加data.it参数校验，同时初始化PeerRoom中缺失的结构。

报错2原因与修复 #

• 原因：客户端发送send命令时未携带mj字段，data.mj为undefined，执行JSON.parse(undefined)触发语法错误；未处理JSON解析失败的情况。
• 修复：校验data.mj是否存在且为合法字符串，对JSON解析增加异常捕获。

修复后的完整服务端代码 #

socket.on("broadcasting", (data) => {
    if (typeof data !== "object" || data === null) {
        return;
    }

    if (!UserInfo[socket.id]) {
        return;
    }

    const userRoom = UserInfo[socket.id].idroom;
    if (!userRoom || !PeerRoom[userRoom]) {
        return;
    }

    if (data.cmd === "new") {
        if (!data.it) {
            socket.emit("msg", {
                cmd: "not",
                data: {
                    topic: "",
                    force: 1,
                    msg: "缺少必要参数：it",
                    user: "",
                },
            });
            return;
        }

        if (UserInfo[socket.id].rep >= SiteSetting["miclikes"]) {
            if (!PeerRoom[userRoom][data.it]) {
                PeerRoom[userRoom][data.it] = { id: "", ev: false };
            }
            io.to(userRoom).emit("broadcasting", { cmd: "new", it: data.it, user: socket.id });
            socket.emit("broadcasting", { cmd: "new", it: data.it });
            PeerRoom[userRoom][data.it].id = socket.id;
            PeerRoom[userRoom][data.it].ev = true;
        } else {
            socket.emit("msg", {
                cmd: "not",
                data: {
                    topic: "",
                    force: 1,
                    msg: `${SiteSetting["miclikes"]}  عدد الايكات المطلوبة للمايك`,
                    user: "",
                },
            });
        }
    } else if (data.cmd === "send") {
        if (!data.mj || typeof data.mj !== "string") {
            socket.emit("msg", {
                cmd: "not",
                data: {
                    topic: "",
                    force: 1,
                    msg: "缺少有效参数：mj",
                    user: "",
                },
            });
            return;
        }

        let myfr;
        try {
            myfr = JSON.parse(data.mj);
        } catch (err) {
            socket.emit("msg", {
                cmd: "not",
                data: {
                    topic: "",
                    force: 1,
                    msg: "mj参数不是合法的JSON格式",
                    user: "",
                },
            });
            return;
        }

        if (!myfr.type) {
            socket.emit("msg", {
                cmd: "not",
                data: {
                    topic: "",
                    force: 1,
                    msg: "缺少必要字段：type",
                    user: "",
                },
            });
            return;
        }

        if (myfr.type === "new-ice-candidate") {
            if (!myfr.target || !myfr.it || !myfr.candidate) {
                socket.emit("msg", { cmd: "not", data: { topic: "", force:1, msg: "new-ice-candidate缺少必要参数", user:"" } });
                return;
            }
            socket.to(myfr.target).emit("broadcasting", {
                cmd: "send",
                msgString: JSON.stringify({
                    type: myfr.type,
                    it: myfr.it,
                    target: myfr.target,
                    user: socket.id,
                    candidate: myfr.candidate,
                }),
            });
        } else if (myfr.type === "video-offer") {
            if (!myfr.target || !myfr.it || !myfr.sdp) {
                socket.emit("msg", { cmd: "not", data: { topic: "", force:1, msg: "video-offer缺少必要参数", user:"" } });
                return;
            }
            socket.to(myfr.target).broadcast.emit("broadcasting", {
                cmd: "send",
                msgString: JSON.stringify({
                    type: myfr.type,
                    it: myfr.it,
                    target: myfr.target,
                    sdp: myfr.sdp,
                    user: socket.id,
                }),
            });
        } else if (myfr.type === "hang-up") {
            if (!myfr.it) {
                socket.emit("msg", { cmd: "not", data: { topic: "", force:1, msg: "hang-up缺少必要参数：it", user:"" } });
                return;
            }
            if (PeerRoom[userRoom][myfr.it]) {
                PeerRoom[userRoom][myfr.it].id = "";
                PeerRoom[userRoom][myfr.it].ev = false;
                io.to(userRoom).emit("broadcasting", { cmd: "send", msgString: data.mj });
            }
        } else if (myfr.type === "video-answer") {
            if (!myfr.target || !myfr.it || !myfr.sdp) {
                socket.emit("msg", { cmd: "not", data: { topic: "", force:1, msg: "video-answer缺少必要参数", user:"" } });
                return;
            }
            socket.to(myfr.target).emit("broadcasting", {
                cmd: "send",
                msgString: JSON.stringify({
                    type: myfr.type,
                    it: myfr.it,
                    target: myfr.target,
                    sdp: myfr.sdp,
                    user: socket.id,
                }),
            });
        } else {
            io.to(userRoom).emit("broadcasting", { cmd: "send", msgString: data.mj });
        }
    }
});

额外优化说明 #

1. 全流程增加参数校验，避免客户端缺失参数导致服务端崩溃
2. 对JSON解析增加try-catch，捕获非法JSON格式异常
3. 提取userRoom变量，减少重复代码调用
4. 统一参数缺失时的错误提示逻辑，提升用户反馈清晰度

内容的提问来源于stack exchange，提问作者jack jeson