TypeScript调用Steam市场API报400 Session mismatch，Python正常

我用TypeScript调用Steam社区市场的sellitem接口售卖物品时，持续收到400响应，错误信息为“Session mismatch”，但用Python实现完全相同的请求逻辑却能正常返回200。以下是相关代码和请求详情，以及问题的解决方法：

可正常运行的Python代码 #

session = requests.Session()

cookies = { "sessionid": "XXX", "steamLoginSecure": "X%7C%XX.X.X", }

session.cookies.update(cookies)

def sellSteamMarketItem(cookie): 
    url = "https://steamcommunity.com/market/sellitem/"

    HEADERS = {
        "Referer": "https://steamcommunity.com/profiles/XXXXXX/inventory"
    }
    session_body = session.post("https://steamcommunity.com/market/sellitem/", data={
        "sessionid": "XXXXX", 
        "appid": "730",                          # App-ID（例如CS:GO）
        "contextid": "2",                        # 库存上下文ID
        "assetid": "XXXX",                       # 物品ID
        "amount": "1",                           # 数量
        "price": "149999"                        
    }, headers=HEADERS)

    if session_body.status_code != 200: 
        print("Error, Statuscode: ", session_body.status_code)

Python请求详情 #

<PreparedRequest [POST]>
HTTP方法: POST
URL: https://steamcommunity.com/market/sellitem/
Headers: 
{
    'User-Agent': 'python-requests/2.32.3',
    'Accept-Encoding': 'gzip, deflate, br',
    'Accept': '*/*',
    'Connection': 'keep-alive',
    'Referer': 'https://steamcommunity.com/profiles/XXXXX/inventory',
    'Cookie': 'sessionid=<REDACTED>; steamLoginSecure=<REDACTED>',
    'Content-Length': '98',
    'Content-Type': 'application/x-www-form-urlencoded'
}
Body: sessionid=<REDACTED>&appid=730&contextid=2&assetid=XXXXX&amount=1&price=149999

出现问题的TypeScript代码 #

create(assetId: number, price: number) {
        let url: string = "https://steamcommunity.com/market/sellitem/";
        const data = {
            sessionid: sessionid,
            appid: "730",                          
            contextid: "2",                        
            assetid: assetId.toString(),               
            amount: "1",                           
            price: price.toString(),                      
        };
        const referer = "https://steamcommunity.com/profiles/" + steamID.getSteamID64() + "/inventory";
        const respone = sendRequest(url, data, referer);
        console.log(respone);
     
    }

async sendRequest(url, params, referer) {
    const headers = {
                        "Cookie": cookies, 
                        "User-Agent": "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/58.0.3029.110 Safari/537.36",
                        "Accept": "application/json, text/plain, */*",
                        "Accept-Encoding": "gzip, deflate, br",
                        "Connection": "keep-alive",
                        "Referer": referer
                    };
    response = await axios.post(url, params, {
                            headers: headers
                        });
}

Axios 400响应详情 #

{
  "headers": {
    "Accept": "application/json, text/plain, */*",
    "Content-Type": "application/json",
    "Cookie": "sessionid=XX; steamLoginSecure=XX;",
    "User-Agent": "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/58.0.3029.110 Safari/537.36",
    "Accept-Encoding": "gzip, deflate, br",
    "Connection": "keep-alive",
    "Referer": "https://steamcommunity.com/profiles/XX/inventory",
    "Content-Length": "123"
  },
  "method": "post",
  "url": "https://steamcommunity.com/market/sellitem/",
  "data": {
    "sessionid": "XX",
    "appid": "730",
    "contextid": "2",
    "assetid": "XX",
    "amount": "1",
    "price": "14555"
  }
}


{
  "data": {
    "success": false,
    "message": "Session mismatch"
  },
  "status": 400
}

问题原因及解决方法 #

核心问题 #

Axios默认会把请求体序列化为JSON格式（Content-Type: application/json），而Python的requests.post使用data参数时，会自动采用application/x-www-form-urlencoded表单编码格式。Steam的sellitem接口仅接受表单编码的请求体，因此JSON格式的请求会触发Session验证失败，返回"Session mismatch"。

解决步骤 #

将Axios的请求体转换为表单编码格式，以下两种方式任选其一：

方式一：使用URLSearchParams构造请求体

修改sendRequest函数：

async sendRequest(url, params, referer) {
    const headers = {
        "Cookie": cookies, 
        "User-Agent": "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/58.0.3029.110 Safari/537.36",
        "Accept": "*/*", // 建议和Python保持一致，减少请求头差异
        "Accept-Encoding": "gzip, deflate, br",
        "Connection": "keep-alive",
        "Referer": referer,
        "Content-Type": "application/x-www-form-urlencoded" // 显式指定表单编码
    };
    // 将参数转换为表单格式
    const formData = new URLSearchParams();
    Object.entries(params).forEach(([key, value]) => {
        formData.append(key, value);
    });
    const response = await axios.post(url, formData, { headers: headers });
    return response;
}

方式二：使用qs库序列化数据

先安装依赖：npm install qs，再修改sendRequest函数：

import qs from 'qs';

async sendRequest(url, params, referer) {
    const headers = {
        "Cookie": cookies, 
        "User-Agent": "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/58.0.3029.110 Safari/537.36",
        "Accept": "*/*",
        "Accept-Encoding": "gzip, deflate, br",
        "Connection": "keep-alive",
        "Referer": referer,
        "Content-Type": "application/x-www-form-urlencoded"
    };
    // 序列化参数为表单格式
    const serializedData = qs.stringify(params);
    const response = await axios.post(url, serializedData, { headers: headers });
    return response;
}

额外注意事项 #

• 确保sessionid在Cookie和请求体中的值完全一致，无额外空格或字符；
• 尽量对齐Python请求的Accept头为*/*，减少不必要的请求差异。

内容的提问来源于stack exchange，提问作者UsAA12