c - 服务器端输出奇怪的字符

Question

当我将输出文件从客户端发送到服务器时，我的输出文件中有一堆奇怪的字符。当我将服务器流式传输到数组并将其打印出来时，它看起来不错且清晰。然而，当我将其发送到服务器时，我在文本文档中到处都看到了一堆奇怪的字符和 MICROSOFT。有人知道出了什么问题吗？

客户:

if(sendSize <=0){
    for(;;){
        unsignedchar buff[256]={0};
        int nread = fread(buff,1,256, fp);

        total = total + nread;
        percentage =(total / fFileSize)*100;
        printf("\r%s: Percentage sent: %.2f", NAME_C, percentage);
        /* Send data in 256 byte chunks */
        if(nread >0){
            send(clientSock, buff, nread, 0);
        }

        if(nread <256){
            if(feof(fp)){
                printf("\nSend Success!\n");
                break;
            }
        }
    }
    //printf("%.2f", total);
}

服务器:

/* Receive data from client */
    char* fileName ="test.txt";
    FILE*fp = fopen(fileName,"w+");;

    float total =0;
    float bytesReceived;
    unsignedchar buff[256]={0};
    float percentage =(bytesReceived / total)*100;

    while((bytesReceived = recv(listenSock, buff,sizeof(buff),0))<0){
        //bytesReceived = recv(listenSock, buff, 256, 0);
        if(bytesReceived >0){
            printf("DONE");
        }
        //total = total + bytesReceived;
        fwrite(buff,sizeof(char), bytesReceived, fp);
        //printf("\r%s: Percentage received: %.2f", NAME_C, percentage);
    }

Answer 1

您的服务器的recv()循环正在使用 <0什么时候应该使用 >0反而。 recv()出错时返回 -1，正常断开连接时返回 0，收到字节时返回 >0。

另外，是listenSock实际监听的套接字，或者 accept() 返回的套接字？您应该将后者传递给 recv() 。我的猜测是你正在传递前者，导致 recv()失败并返回 -1，然后使用垃圾 buff 进入循环体数据又不好bytesReceived值(value)。第三个参数fwrite()是 size_t ，这是一个无符号类型，因此传递 -1 有符号值将被解释为 4294967295 的无符号值甚至 18446744073709551615 ，取决于 size_t 的大小。无论哪种方式，您都会向文件中写入垃圾，甚至会导致尝试访问无效内存的代码崩溃。

您的代码还存在其他小问题。尝试更像这样的东西:

客户:

if(sendSize <=0){
    unsigned char buff[256];
    do{
        int nread = fread(buff, sizeof(char), 256, fp);
        if (nread > 0){
            total += nread;
            percentage = (total / fFileSize)*100;
            printf("\r%s: Percentage sent: %.2f", NAME_C, percentage);
            /* Send data in 256 byte chunks */
            if (send(clientSock, buff, nread, 0) == -1){
                printf("\nSend Failed!\n");
                break;
            }
        }
        if (nread != 256){
            if (feof(fp)){
                printf("\nSend Success!\n");
            else
                printf("\nRead Failed!\n");
            break;
        }
    }
    while (1);
    //printf("%.2f", total);
}

服务器:

/* Receive data from client */
char* fileName = "test.txt";
FILE* fp = fopen(fileName, "wb+");
if (!fp){
    printf("\nOpen Failed!\n");
}
else{
    float total = 0;
    float percentage = 0;
    int bytesReceived;
    unsigned char buff[256];

    do{
        bytesReceived = recv(acceptedSock, buff, sizeof(buff), 0);
        if (bytesReceived <= 0){
            if (bytesReceived < 0){
                printf("\nRecv Failed!\n");
            }
            else{
                printf("\nDisconnected!\n");
            }
            break;
        }
        //total += bytesReceived;
        //percentage = ...
        if (fwrite(buff, sizeof(char), bytesReceived, fp) != bytesReceived){
            printf("\nWrite Failed!\n");
            break;
        }
        //printf("\n%s: Percentage received: %.2f", NAME_C, percentage);
    }
    while (1);
}