我正在尝试将文件从客户端发送到服务器。它有时起作用,有时不起作用。第一次尝试发送文件时,它将发送损坏的文件,并且在服务器端形成的文件端是其大小的两倍。但是,首次尝试后,所有尝试的文件都成功传输。谁能帮我这个 ?
客户端
message msg;
msg.type = SEND_FILE;
char *username, *filename;
username = strtok(input+6, " ");
filename = strtok(NULL, "");
//Get Picture Size
printf("Getting Picture Size\n");
FILE *picture;
picture = fopen(filename, "r");
int size;
fseek(picture, 0, SEEK_END);
size = ftell(picture);
fseek(picture, 0, SEEK_SET);
//Send Picture Size
printf("Getting Picture Size\n");
sprintf(msg.data, "%d", size);
strncpy(msg.username, username, 20);
if(send(connection->socket, &msg, sizeof(message), 0) < 0)
{
perror("Send failed");
exit(1);
}
//Send Picture as Byte Array
printf("Sending Picture as Byte Array\n");
char send_buffer[size+1];
fread(send_buffer, 1, sizeof(send_buffer), picture);
write(connection->socket, send_buffer, sizeof(send_buffer));
bzero(send_buffer, sizeof(send_buffer));
服务器
//Read Picture Size
printf("Reading Picture Size\n");
int size = atoi(message_text);
//Read Picture Byte Array
printf("Reading Picture Byte Array\n");
char p_array[size];
printf("Converting Byte Array to Picture %d\n", size);
FILE *image;
image = fopen("c4.png", "w");
int readSize = 0;
while (readSize < size) {
readSize = readSize + read(clients[sender].socket, p_array, size);
fwrite(p_array, 1, sizeof(p_array), image);
}
fclose(image);
对于初学者:
您不想在每个字节上存储相同数量的字节 fwrite()
fwrite(p_array, 1, sizeof(p_array), image);
但仅实际读取的字节数。
sizeof(p_array)
返回的大小p_array
,该大小是size
的大小的乘积char
。后者定义为1
。
除此之外,对的调用read()
完全没有错误检查,还测试了另一端是否关闭了连接。这并不遥不可及。
要解决此问题,您可以执行以下操作:
#include <errno.h> /* for errno */
...
size_t size = atoi(message_text);
printf("Reading Picture Byte Array\n");
char p_array[size];
size_t readSize = 0;
while (readSize < size) {
ssize_t result = read(clients[sender].socket, p_array, size); /* Mind the ssize_t, it's *not* size_t! */
if (0 >= result)
{
if (0 == result)
{
fprintf(stderr, "The other end gracefully shut down the connection.\n");
break;
}
else
{
if (EINTR == errno) /* got interrupted, start over */
{
continue;
}
if (EAGAIN == errno) /* in case reading from a non-blocking socket: no data available, start over */
{
continue;
}
/* Something went wrong unrecoverable. */
perror("read() failed");
break;
}
}
else
{
fwrite(p_array, 1, result, image);
/* Also add error checking here! */
readSize += result;
}
}
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