C 通过套接字发送后，文件大小会发生变化

通过套接字将文件从客户端发送到服务器时，文件大小会发生变化。问题出在哪里

以下是客户端代码：

char chunk[512];
host_info = gethostbyname(server);
if (host_info == NULL) {
    perror("get host by name");
    exit(errno);
}

socket_desc = socket(AF_INET, SOCK_STREAM, 0);
if (socket_desc < 0) {
    perror("socket");
    exit(errno);
}

server_address.sin_family = host_info->h_addrtype;
memcpy((char *) &server_address.sin_addr.s_addr, host_info->h_addr_list[0], host_info->h_length);
server_address.sin_port = htons(PORT);

if (connect(socket_desc, (struct sockaddr *) &server_address, sizeof(server_address)) < 0) {
    perror("connect");
    exit(errno);
}


file_to_send = fopen (lfile,"rb");
if(!file_to_send) {
    perror("fopen");
    close(socket_desc);
    exit(errno);
} else {
    long file_size;
    fseek (file_to_send, 0, SEEK_END);     
    file_size = ftell (file_to_send);
    rewind(file_to_send);
while(totally_read < file_size){
    chunk[0] = '\0';
    bytes_read = fread(chunk, sizeof(char), sizeof(chunk), file_to_send);
    totally_read += bytes_read;
    int sent = send(socket_desc, chunk, bytes_read, 0);
    if(sent < 0){
        perror("connect");
        exit(errno);
    }
    totally_sent += sent;
    printf("read: %7db sent: %7db totally read: %7db totally sent: %7db\n", bytes_read, sent, totally_read, totally_sent);
}

但在服务器端：

char chunk[512];
listen_socket = socket(AF_INET, SOCK_STREAM, 0);
if (listen_socket < 0) {
    perror("socket");
    close(listen_socket);
    exit(errno);
}

server_address.sin_family = AF_INET;
server_address.sin_addr.s_addr = htonl(INADDR_ANY);
server_address.sin_port = htons(PORT);

if (bind(listen_socket, (struct sockaddr *) &server_address, sizeof(server_address)) < 0) {
    perror("bind");
    close(listen_socket);
    exit(errno);
}

listen(listen_socket, 5);
client_address_length = sizeof(client_address);

while(1){    
    connect_socket = accept(listen_socket, (struct sockaddr *) &client_address, &client_address_length);
    if (connect_socket < 0) {
    perror("accept");
    close(listen_socket);
    exit(errno);
}

recv_file = fopen(filename,"wb");
int received = 0;
int totally_wrote = 0, totally_received = 0;
while(1){
    chunk[0] = '\0';
    received = recv(connect_socket, chunk, sizeof(chunk), 0);
    if(received < 0) {
        perror("recv");
    } else if(received > 0) {
        int wrote = fwrite(chunk, sizeof(char), received, recv_file);
        totally_wrote +=wrote;
        totally_received += received;
        printf("received: %7db wrote: %7db totally received: %7db torally wrote: %7db\n", received, wrote, totally_received, totally_wrote);
    } else {
        printf("Complete!\n");
        break;
    }
}

totally received:  303279b   |   torally wrote:  303279b

---

我已经用编辑器打开了文件。传输的文件实际上与源文件相同，只是开始时有一些奇怪的数据。如果数据块大小为512字节，则传输的文件在开始时将包含3584字节的ADDICTIONSL二进制数据。如果我将块大小更改为256字节，它将增加3840字节。

您没有检查send（）的返回值 Send（）可以返回-1和第三个（长度）参数之间的任何值，包括-1和第三个（长度）参数。假设任何大于0的返回值都等于第三个参数。它们不必如此

要处理短send（）s（或recv（）s（或read（）/write（）），您需要以下内容：

int sent, pos, bytes_read;
bytes_read = fread(chunk, sizeof(char), sizeof(chunk), file_to_send);

totally_read += bytes_read;

for (pos = 0; pos < bytes_read; pos += sent) {
    sent = send(socket_desc, chunk+pos, bytes_read-pos, 0)
    switch(sent) {
    case -1: /* handle errno here, especially EAGAIN/EINTR */
    case 0: /*handle EOF here */
        break;
    default:
        break;
        }
    }
totally_sent += pos;

int发送，pos，字节读取；
bytes_read=fread（块、大小（char）、大小（块）、文件发送）；
总读取+=字节读取；
用于（pos=0；pos

你确定没有其他进程访问同一个文件。你可以使用

lsof

来检查

chunk

是如何声明的？用

gcc-Wall-g

编译你的代码，直到没有警告为止，然后用

gdb

调试你的程序。我刚刚测试了你所有的代码，它工作正常。（我只是需要添加fclose（recv_file）来刷新）可能您在变量声明中有错误，或者在这类事情中有错误…还可以看看

sendfile

Downvote，因为它没有提供所有相关的代码。请参阅OP自己的答案。发送时没有EOF这样的事情。事实上，没有short send（）这样的事情无论是在阻塞模式。

int sent, pos, bytes_read;
bytes_read = fread(chunk, sizeof(char), sizeof(chunk), file_to_send);

totally_read += bytes_read;

for (pos = 0; pos < bytes_read; pos += sent) {
    sent = send(socket_desc, chunk+pos, bytes_read-pos, 0)
    switch(sent) {
    case -1: /* handle errno here, especially EAGAIN/EINTR */
    case 0: /*handle EOF here */
        break;
    default:
        break;
        }
    }
totally_sent += pos;