c - C : Data not being sent/received properly? 中的服务器/套接字编程

Question

我正在编写一个监听连接的服务器端程序。当它收到一个时，它会产生一个分离的线程并处理连接。我希望它能够接收从客户端发送的多行数据，并将其存储在数据结构中(这样我可以稍后对其进行排序)。

客户端这样做:

1. 获取 .csv 文件的文件大小
2. 将文件大小发送到服务器
3. 打开.csv
4. 使用 fgets() 检索一行并将其放入缓冲区
5. 将这一行的字节数发送到服务器
6. 将线路数据发送到服务器

目标是逐行发送数据，并将每一行存储在服务器端的结构中。问题是，数据没有被发送过来。似乎单个发送请求被切断并在两个不同的 recv() 调用中处理。

客户端发送循环:

void sendData(int sock, FILE* fd){
    char data[BUFFER];
    int32_t filesize;

    printf("seeking\n");
    if((fseek(fd, 0L, SEEK_END)) == ERROR){
        fprintf(stderr, "An error has occured: %s\n", strerror(errno));
        exit(EXIT_FAILURE);
    };
    if((filesize = ftell(fd)) == ERROR){
        fprintf(stderr, "An error has occured: %s\n", strerror(errno));
        exit(EXIT_FAILURE);
    };
    rewind(fd);

    // subtracting bytes for the col headers 
    //filesize -= COLSIZE;
    fgets(data, sizeof(data), fd);
    printf("strlen of data: %d\n", (int)strlen(data));
    printf("\nfilesize: %ld\n", (long)filesize);
    filesize = filesize - strlen(data);
    printf("\nfilesize: %ld\n", (long)filesize);
    // converting data len to net order
    filesize = htonl(filesize);
    char* len_data = (char*)&filesize;
    // sending filesize
    printf("sending filesize\n");
    send(sock, len_data, sizeof(int32_t), 0);
    filesize = ntohl(filesize);
    printf("\nfilesize: %ld\n", (long)filesize);

    // grabbing first line and sending
    //printf("fgetting test\n");
    while(filesize > 0){
        while(fgets(data, sizeof(data), fd) != NULL){
            if(data[strlen(data) - 1] == '\n'){
                printf("\ntaking newline out\n");
                data[strlen(data) - 1] = '\0';
            }

            // getting and sending size of the line
            int32_t dataSize = sizeof(char)*strlen(data);
            printf("data size of line: %d\n", dataSize);
            dataSize = htonl(dataSize);
            char* lineSize = (char*)&dataSize;
            int j = send(sock, lineSize, sizeof(int32_t), 0);
            printf("size of data sent: %d\n", j);

            // sending the line
            printf("line of data: %s\n", data);
            int i = send(sock, data, sizeof(char)*strlen(data), 0);
            printf("size of data sent: %d\n", i);
            filesize -= i;
            printf("new filesize: %d\n", filesize);
        }
    }

客户端输出:

taking newline out
data size of line: 303                                                                                               
size of data sent: 4                                                                                                 
line of data: Color,Andrew Stanton,462,132,475,530,Samantha Morton,640,73058679,Action|Adventure|Sci-Fi,Daryl Sabara,John Carter ,212204,1873,Polly Walker,1,alien|american civil war|male nipple|mars|princess,http://www.imdb.com/title/tt0401729/?ref_=fn_tt_tt_1,738,English,USA,PG-13,263700000,2012,632,6.6,2.35,24000
size of data sent: 303
new filesize: 1001

服务器接收循环:

    int32_t linesize;
    int32_t filesize;
    // set to 1 to attempt to receive bytes
    receive_int(&filesize,sock_info->sock);
    printf("Recieving file size %d\n", filesize);
    // wait for a recv
    while(filesize){

        printf("\nCurrent File Size: %ld\n",(long) filesize);
        receive_int(&linesize,sock_info->sock);
        printf("Line size: %ld\n", (long)linesize);
        char* filebuf = (char*)malloc(sizeof(char)*linesize);
        printf("size of filebuf: %d\n", sizeof(*filebuf));
        int i = recv(sock_info->sock, filebuf, sizeof(char)*linesize, 0);
        printf("strlen of filebuf: %d\n", strlen(filebuf));
        printf("number of bytes received: %d\n", i);
        printf("Received msg: %s\n",filebuf);
        filesize -= i;


    }

服务器输出

Current File Size: 1304                                                                                              
Line size: 303                                                                                                       
size of filebuf: 1                                                                                                   
strlen of filebuf: 165                                                                                               
number of bytes received: 165                                                                                        
Received msg: Color,Andrew Stanton,462,132,475,530,Samantha Morton,640,73058679,Action|Adventure|Sci-Fi,Daryl Sabara,John Carter ,212204,1873,Polly Walker,1,alien|american civil                          

Current File Size: 1139                                                                                              
Line size: 2002875004                                                                                                
size of filebuf: 1                                                                                                   
strlen of filebuf: 134                                                                                               
number of bytes received: 1139
Received msg: male nipple|mars|princess,http://www.imdb.com/title/tt0401729/?ref_=fn_tt_tt_1,738,English,USA,PG-13,263700000,2012,632,6.6,2.35,24000

Answer 1

如 recv 的 man 页面所示:

The receive calls normally return any data available, up to the requested amount, rather than waiting for receipt of the full amount requested.

如 man 页面中的 send 所示:

With a zero flags argument, send() is equivalent to write(2). ... On success, these calls return the number of bytes sent.

如 man 页面中的 write 所示:

writes up to count bytes from the buffer starting at...

如您所见，网络 send 和 recv 不保证实际发送的数据长度或每个接收数据的长度函数调用。

此外，当数据包在网络中移动时，单个数据包被分成多个数据包(例如，由于网络 MTU 设置的差异)是很常见的。

处理网络数据的唯一方法是将其视为连续流。

为了找到换行标记，接收端点必须连接所有接收到的数据并沿着换行标记将其切割。

我推荐Beej's guide作为启动网络编码的良好资源。

祝你好运。