C uses TCP protocol for file transfer TOC
How to achieve it
1. The server program creates a TCP server socket, binds it to a specific IP address and port, and starts listening to the client’s connection request.
2. The client program creates a TCP client socket and connects to the server’s IP address and port.
3. The client sends the name of the file to be transferred to the server. After receiving the file name, the server judges whether the file exists. If it exists, it replies to the client and sends the file size to the client.
4. After the client receives the reply from the server and obtains the file size, it starts sending the file data. The client can read the file data through a loop, and call the send() function to send the data to the server.
5. After the server receives the data sent by the client, it writes the data into the file. The server can receive data through a loop, and call the write() function to write the data to a file.
6. After the client has sent all the data, close the socket and notify the server that the file transfer has been completed. After receiving the data sent by the client, the server closes the socket.
Note
1. In the process of file transfer, the integrity and accuracy of the data need to be considered, and the correctness of the transferred data can be verified by calculating the checksum or using the hash algorithm.
2. When the file to be transferred is large, it needs to be transferred in batches, which can be carried out by means of block transfer.
3. Before the data is transmitted, the data needs to be encapsulated and some meta information is added for transmission control and data verification.
4. When writing programs, it is necessary to consider issues such as network delay and packet loss, and use appropriate methods for retransmission or compensation.
5. Issues such as data security and encryption and decryption during transmission need to be considered when transferring files.
Upload the code directly
Server program:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <unistd.h>
#define PORT 8888
int main()
{<!-- -->
int server_fd, new_socket, valread;
struct sockaddr_in address;
int opt = 1;
int addrlen = sizeof(address);
// create TCP server socket
if ((server_fd = socket(AF_INET, SOCK_STREAM, 0)) == 0)
{<!-- -->
perror("socket failed");
exit(EXIT_FAILURE);
}
// Set socket options to allow reuse of address and port
if (setsockopt(server_fd, SOL_SOCKET, SO_REUSEADDR | SO_REUSEPORT,
&opt, sizeof(opt)))
{<!-- -->
perror("setsockopt");
exit(EXIT_FAILURE);
}
// set address and port
address.sin_family = AF_INET;
address.sin_addr.s_addr = INADDR_ANY;
address.sin_port = htons(PORT);
// bind the socket to a specific address and port
if (bind(server_fd, (struct sockaddr *) & address,
sizeof(address)) < 0)
{<!-- -->
perror("bind failed");
exit(EXIT_FAILURE);
}
// Start listening for client connection requests
if (listen(server_fd, 3) < 0)
{<!-- -->
perror("listen");
exit(EXIT_FAILURE);
}
printf("Waiting for connections...\\
");
// wait for client connection
if ((new_socket = accept(server_fd, (struct sockaddr *) & amp;address,
(socklen_t *) & amp; addrlen)) < 0)
{<!-- -->
perror("accept");
exit(EXIT_FAILURE);
}
printf("Connection accepted.\\
");
// Receive the file name sent by the client
char filename[1024];
valread = read(new_socket, filename, 1024);
if (valread < 0)
{<!-- -->
perror("read");
exit(EXIT_FAILURE);
}
printf("Received filename: %s\\
", filename);
// open the file and get the file size
FILE *fp;
if ((fp = fopen(filename, "rb")) == NULL)
{<!-- -->
perror("fopen");
exit(EXIT_FAILURE);
}
fseek(fp, 0, SEEK_END);
int file_size = ftell(fp);
fseek(fp, 0, SEEK_SET);
// Reply to the client and send the file size
char filesize_str[32];
sprintf(filesize_str, "%d", file_size);
valread = send(new_socket, filesize_str, strlen(filesize_str), 0);
if (valread < 0)
{<!-- -->
perror("send");
exit(EXIT_FAILURE);
}
// send file data
char buffer[1024];
int bytes_read;
while ((bytes_read = fread(buffer, 1, 1024, fp)) > 0)
{<!-- -->
if (send(new_socket, buffer, bytes_read, 0) != bytes_read)
{<!-- -->
perror("send");
exit(EXIT_FAILURE);
}
}
fclose(fp);
close(new_socket);
close(server_fd);
printf("File transfer completed.\\
");
return 0;
}
Client program:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <unistd.h>
#define PORT 8888
int main(int argc, char const *argv[])
{<!-- -->
int sock = 0, valread;
struct sockaddr_in serv_addr;
char buffer[1024] = {<!-- -->0};
// Create a TCP client socket
if ((sock = socket(AF_INET, SOCK_STREAM, 0)) < 0)
{<!-- -->
printf("\\
Socket creation error \\
");
return -1;
}
memset( &serv_addr, '0', sizeof(serv_addr));
serv_addr.sin_family = AF_INET;
serv_addr.sin_port = htons(PORT);
// Convert the IP address from dotted decimal to binary form
if (inet_pton(AF_INET, "127.0.0.1", &serv_addr.sin_addr) <= 0)
{<!-- -->
printf("\\
Invalid address/ Address not supported \\
");
return -1;
}
// connect to server
if (connect(sock, (struct sockaddr *) & amp;serv_addr, sizeof(serv_addr)) < 0)
{<!-- -->
printf("\\
Connection Failed \\
");
return -1;
}
// send filename
char *filename = "test.jpg";
valread = send(sock, filename, strlen(filename), 0);
if (valread < 0)
{<!-- -->
perror("send");
return -1;
}
// receive file size
char filesize_str[32];
valread = read(sock, filesize_str, 32);
if (valread < 0)
{<!-- -->
perror("read");
return -1;
}
int file_size = atoi(filesize_str);
// receive file data
FILE *fp;
if ((fp = fopen("recv.jpg", "wb")) == NULL)
{<!-- -->
perror("fopen");
return -1;
}
int bytes_received = 0;
int bytes_left = file_size;
while (bytes_left > 0)
{<!-- -->
int bytes_to_receive = bytes_left < 1024 ? bytes_left : 1024;
bytes_received = read(sock, buffer, bytes_to_receive);
if (bytes_received < 0)
{<!-- -->
perror("read");
return -1;
}
fwrite(buffer, 1, bytes_received, fp);
bytes_left -= bytes_received;
}
fclose(fp);
close(sock);
printf("File transfer completed.\\
");
return 0;
}