Example of simple socket File Download Based on C in Linux

This instance is used by the client to download files from the server:

ServerCodeImplementation:

# Include <stdio. h>
# Include <stdlib. h>
# Include <string. h>
# Include <sys/types. h>
# Include <sys/socket. h>
# Include <sys/STAT. h>
# Include <unistd. h>
# Include <ARPA/inet. h>
# Include <errno. h>
# Include <fcntl. h>

# Define fd_server_port 8088/* set port */
# Define fd_buffersize 1024/* Set buffer size */
# Define fd_listenq 10/* Set listen Max conncent */

Int main (INT argc, char * argv [])
{
Int fd_listenfd, fd_connfd, fd_filefd;/* descriptor */
Int fd_read, fd_write;
Int struct_size;
Struct sockaddr_in fd_servaddr, fd_cliaddr;
Char * fd_filename;
Char * P;
Char buffer [fd_buffersize];

Fd_listenfd = socket (af_inet, sock_stream, 0);/* Create socket */
If (fd_listenfd =-1 ){
Perror ("fd_socket ");
Exit (1 );
}

Memset (& fd_servaddr, 0, sizeof (fd_servaddr);/* servaddr set 0 */

Fd_servaddr.sin_family = af_inet;/* init serveraddr */
Fd_servaddr.sin_addr.s_addr = inaddr_any;
Fd_servaddr.sin_port = htons (fd_server_port );

/* Bind fd_listenfd */

If (-1 = (BIND (fd_listenfd, (struct sockaddr *) & fd_servaddr, sizeof (fd_servaddr )))){
Perror ("fd_bind ");
Exit (1 );
}

/* Listen fd_listenfd */
If (-1 = (Listen (fd_listenfd, fd_listenq ))){
Perror ("fd_listen ");
Exit (1 );
}

/* File download server start */
While (1 ){
Printf ("file download server starting... \ n ");

Memset (& fd_cliaddr, 0, sizeof (fd_cliaddr ));
Struct_size = sizeof (fd_cliaddr );

Fd_connfd = accept (fd_listenfd, (struct sockaddr *) & fd_cliaddr, & struct_size );
If (-1 = fd_connfd ){
Perror ("fd_accpet ");
Continue;
}

Fd_filename = "/root/tmp.txt ";
Printf ("will download file name is: % s \ n", fd_filename );
Fd_filefd = open (fd_filename, o_rdonly );
If (-1 = fd_filefd ){
Perror ("Open will download file ");
Continue;
}
While (fd_read = read (fd_filefd, buffer, fd_buffersize )){
If (-1 = fd_read ){
Perror ("read will download file ");
Break;
}

P = buffer;
While (fd_write = write (fd_connfd, P, fd_read )){
If (-1 = fd_write ){
Perror ("write client file ");
Break;
}
Else if (fd_read = fd_write) break;
Else if (fd_write> 0 ){
P + = fd_write;
Fd_read-= fd_write;
}
}
}
If (-1 = fd_read |-1 = fd_write) continue;
Close (fd_filefd );
Close (fd_connfd );
Printf ("file already is downloaded! \ N ");
}
Close (fd_listenfd );
Return 0;
}

Client code implementation:

# Include <stdio. h>
# Include <stdlib. h>
# Include <string. h>
# Include <sys/types. h>
# Include <sys/socket. h>
# Include <sys/STAT. h>
# Include <unistd. h>
# Include <ARPA/inet. h>
# Include <errno. h>
# Include <fcntl. h>

# Define fd_server_port 8088/* set port */
# Define fd_buffersize 1024/* Set buffer size */

Int main (INT argc, char * argv [])
{
Int fd_sockfd, fd_filefd;/* descriptor */
Int fd_read, fd_write;
Int struct_size;
Struct sockaddr_in fd_sockaddr;
Char * fd_filename;
Char * P;
Char buffer [fd_buffersize];

If (argc! = 2 ){
Perror ("fd_usage: <./client> <Server IP> \ n ");
Exit (1 );
}
Fd_sockfd = socket (af_inet, sock_stream, 0);/* Create socket */
If (fd_sockfd =-1 ){
Perror ("fd_socket ");
Exit (1 );
}

Memset (& fd_sockaddr, 0, sizeof (fd_sockaddr);/* servaddr set 0 */

Fd_sockaddr.sin_family = af_inet;/* init serveraddr */
Inet_aton (argv [1], & fd_sockaddr.sin_addr );
Fd_sockaddr.sin_port = htons (fd_server_port );

If (-1 = (connect (fd_sockfd, (struct sockaddr *) & fd_sockaddr, sizeof (fd_sockaddr )))){
Perror ("fd_connect ");
Exit (1 );
}
Printf ("start connecting... \ n ");

Fd_filename = "./backup.txt ";
Fd_filefd = open (fd_filename, o_rdwr | o_creat | o_trunc, s_irwxu );
If (-1 = fd_filefd ){
Perror ("Open the backup file ");
Exit (1 );
}
While (fd_read = read (fd_sockfd, buffer, fd_buffersize )){
If (-1 = fd_read ){
Perror ("read Server File ");
Exit (1 );
}

/* P is used to wirte Error */
P = buffer;
While (fd_write = write (fd_filefd, P, fd_read )){
If (-1 = fd_write ){
Perror ("Write localhost file ");
Exit (1 );
}
Else if (fd_read = fd_write) break;
Else if (fd_write> 0 ){
P + = fd_write;
Fd_read-= fd_write;
}
}
}
Close (fd_filefd );
Close (fd_sockfd );
Printf ("finsh File Download! \ N ");
Return 0;

}