求助关于局域网 Socket 传送文件时好时坏的问题

硬件背景

Client 树莓派 4B 2G 运行 debian 11 x64 Server Macbook macOS 两者采用有线连接至同一台交换机中

问题表现

在传输文件时有时成功，有时失败。失败时在终端打印乱码，但对于同一文件打印出来的乱码相同，个人猜测是编码问题，但是 debian 和 macOS 用的应该都是 UTF-8 ？而且传字符串没有问题

代码贴图

下面给出 Server 端和 Client 端的代码

//Server 接收端
struct PacketHeader {
    int size;            // 大小：字节
    PacketHeader() {
        size = 0;
    }
};

void *receiveMsg(void *sock) {
    // system("pwd");
    char buffer[1024];
    int *socket = (int *) sock;
    while (1) {
        usleep(500);
        int nRecv = recv(*socket, buffer, 1024, 0);
        if (nRecv <= 0) {
            continue;
        } else if (nRecv == sizeof(PacketHeader)) {
            PacketHeader ph;
            memcpy(&ph, buffer, nRecv);
            cout << "大小：" << ph.size << "Bytes" << endl;
            string filename = ("../Received/" + getCurrentTime() + ".jpg");
            FILE *fp = fopen(filename.c_str(), "wb");
            if (fp == NULL) {
                cout << "file not found" << endl;
            }
            cout << "开始接收图片" << endl;
            nRecv = 0;
            while (nRecv < ph.size) {
                usleep(500);
                memset(buffer, 0, sizeof(buffer));
                int byteCount = recv(*socket, buffer, 1024, 0);
                if (byteCount <= 0) {
                    continue;
                }
                fwrite(buffer, 1, byteCount, fp);
                nRecv += byteCount;
                cout << "已接收 " << nRecv << " Bytes" << endl;
            }
            cout << "共接收 " << nRecv << " Bytes" << endl;
            fclose(fp);
        } else {
            buffer[nRecv] = '\0';
            cout << buffer << endl;
        }
    }
    

# Client 发送端
struct PacketHeader
{
    int size; // 大小：字节
    PacketHeader()
    {
        size = 0;
    }
};

void *sendMsg(void *socket)
{
    int sock = *((int *)socket);
    while (1)
    {
        char msg[4096];
        string filename;
        cin >> filename;
        FILE *fp = fopen(("../image/" + filename).c_str(), "rb");
        if (fp == NULL)
        {
            cout << "file not found" << endl;
            continue;
        }
        int sz = FileSize(("../image/" + filename).c_str());
        cout << "文件打开成功,大小:" << sz << " Bytes" << endl;

        PacketHeader ph;
        ph.size = sz;
        send(sock, (const char *)&ph, sizeof(ph), 0);
        cout << "已发送头部信息" << endl;

        int nSend = 0;
		char buffer[1024];
	    while(nSend < sz)
        {
            int nBytes = fread(buffer, sizeof(char), sizeof(buffer), fp);
            if (nBytes <= 0)
                break;
            send(sock, buffer, nBytes, 0);
            cout << "已发送 " << nBytes << " Bytes" << endl;
            nSend += nBytes;
        }
        cout<<"总计发送 "<<nSend<<" Bytes"<<endl;
		fclose(fp);
        cout << "successfully send " + filename << endl;
    }
}