Linux下各类TCP网络服务器的实现源代码

服务器端代码：

#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <sys/wait.h>

int main(int argc, char**argv)
{
int sockfd, new_fd;
struct sockaddr_in my_addr;
struct sockaddr_in their_addr;

unsigned int sin_size, myport, lisnum;

if(argv[1])
{
myport = atoi(argv[1]);
}
else
{
myport = 7838;
}

if(argv[2])
{
lisnum = atoi(argv[2]);
}
else
{
lisnum = 2;
}

if((sockfd = socket(PF_INET, SOCK_STREAM,0)) == -1)
{
perror("socket");
exit(1);
}

my_addr.sin_family = PF_INET;
my_addr.sin_port = htons(myport);
my_addr.sin_addr.s_addr = INADDR_ANY;
bzero(&(my_addr.sin_zero), 0);

if(bind(sockfd, (struct sockaddr*)&my_addr, sizeof(struct sockaddr)) == -1)
{
perror("bind");
exit(1);
}

if(listen(sockfd, lisnum) == -1)
{
perror("listen");
exit(1);
}

while(1)
{
sin_size = sizeof(struct sockaddr_in);
if((new_fd = accept(sockfd, (struct sockaddr*)&their_addr, &sin_size)) == -1)
{
perror("accept");
continue;
}

printf("server: got connection from %s\n", inet_ntoa(their_addr.sin_addr));

if(!fork())
{
if(send(new_fd, "Hello, world!\n", 14, 0) == -1)
{
perror("send");
close(new_fd);
exit(0);
}
}
close(new_fd);
waitpid(-1, NULL, WNOHANG);
}
}

客户端代码：

#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <netdb.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <sys/socket.h>

#define MAXDATASIZE 100

int main(int argc, char** argv)
{
int sockfd, numbytes;
char buf[MAXDATASIZE];

struct hostent* he;
struct sockaddr_in their_addr;
unsigned int myport;

if(argv[2])
{
myport = atoi(argv[2]);
}
else
{
myport = 7838;
}

if(argc != 3)
{
fprintf(stderr, "usage: %s hostname port\n", argv[0]);
exit(1);
}

if((he = gethostbyname(argv[1])) == NULL)
{
perror("gethostname");
exit(1);
}

if((sockfd = socket(PF_INET, SOCK_STREAM, 0)) == -1)
{
perror("socket");
exit(1);
}

their_addr.sin_family = PF_INET;
their_addr.sin_port = htons(myport);

their_addr.sin_addr = *((struct in_addr*)he->h_addr);
bzero(&(their_addr.sin_zero), 0);

if(connect(sockfd, (struct sockaddr*)&their_addr, sizeof(struct sockaddr)) == -1)
{
perror("connect");
exit(1);
}

if((numbytes = recv(sockfd, buf, MAXDATASIZE, 0)) == -1)
{
perror("recv");
exit(1);
}

buf[numbytes] = 0;
printf("Recevied: %s\n", buf);
close(sockfd);

return 0;
}

I/O复用

#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/time.h>
#include <sys/types.h>
#include <string.h>
#include <signal.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <errno.h>

static int forward_port;

#undef max
#define max(x,y) ((x) > (y) ? (x) : (y))

static int listen_socket (int listen_port) {
struct sockaddr_in a;
int s;
int yes;
if ((s = socket (AF_INET, SOCK_STREAM, 0)) < 0) {
perror ("socket");
return -1;
}
yes = 1;
if (setsockopt(s, SOL_SOCKET, SO_REUSEADDR, (char *) &yes, sizeof (yes)) <
0) {
perror ("setsockopt");
close (s);
return -1;
}
memset (&a, 0, sizeof (a));
a.sin_port = htons (listen_port);
a.sin_family = AF_INET;
if (bind(s, (struct sockaddr *) &a, sizeof (a)) < 0) {
perror ("bind");
close (s);
return -1;
}
printf ("accepting connections on port %d\n", (int) listen_port);
listen (s, 10);
return s;
}

static int connect_socket (int connect_port, char *address) {
struct sockaddr_in a;
int s;
if ((s = socket (AF_INET, SOCK_STREAM, 0)) < 0) {
perror ("socket");
close (s);
return -1;
}

memset (&a, 0, sizeof (a));
a.sin_port = htons (connect_port);
a.sin_family = AF_INET;

if (!inet_aton(address, (struct in_addr *) &a.sin_addr.s_addr)) {
perror ("bad IP address format");
close (s);
return -1;
}

if (connect(s, (struct sockaddr *) &a, sizeof (a)) < 0) {
perror ("connect()");
shutdown (s, SHUT_RDWR);
close (s);
return -1;
}
return s;
}

#define SHUT_FD1 { \
if (fd1 >= 0) { \
shutdown (fd1, SHUT_RDWR); \
close (fd1); \
fd1 = -1; \
} \
}

#define SHUT_FD2 { \
if (fd2 >= 0) { \
shutdown (fd2, SHUT_RDWR); \
close (fd2); \
fd2 = -1; \
} \
}

#define BUF_SIZE 1024

int main (int argc, char **argv) {
int h;
int fd1 = -1, fd2 = -1;
char buf1[BUF_SIZE], buf2[BUF_SIZE];
int buf1_avail, buf1_written;
int buf2_avail, buf2_written;

if (argc != 4) {
fprintf (stderr, "Usage\n\tfwd \n");
exit (1);
}

signal (SIGPIPE, SIG_IGN);

forward_port = atoi (argv[2]);

/*建立监听socket*/
h = listen_socket (atoi (argv[1]));
if (h < 0) exit (1);

for (;;) {
int r, nfds = 0;
fd_set rd, wr, er;
FD_ZERO (&rd);
FD_ZERO (&wr);
FD_ZERO (&er);
FD_SET (h, &rd);

/*把监听socket和可读socket三个一起放入select的可读句柄列表里*/
nfds = max (nfds, h);
if (fd1 > 0 && buf1_avail < BUF_SIZE) {
FD_SET (fd1, &rd);
nfds = max (nfds, fd1);
}
if (fd2 > 0 && buf2_avail < BUF_SIZE) {
FD_SET (fd2, &rd);
nfds = max (nfds, fd2);
}

/*把可写socket两个一起放入select的可写句柄列表里*/
if (fd1 > 0 && buf2_avail - buf2_written > 0) {
FD_SET (fd1, &wr);
nfds = max (nfds, fd1);
}
if (fd2 > 0 && buf1_avail - buf1_written > 0) {
FD_SET (fd2, &wr);
nfds = max (nfds, fd2);
}

/*把有异常数据的socket两个一起放入select的异常句柄列表里*/
if (fd1 > 0) {
FD_SET (fd1, &er);
nfds = max (nfds, fd1);
}
if (fd2 > 0) {
FD_SET (fd2, &er);
nfds = max (nfds, fd2);
}

/*开始select*/
r = select (nfds + 1, &rd, &wr, &er, NULL);

if (r == -1 && errno == EINTR) continue;
if (r < 0) {
perror ("select()");
exit (1);
}

/*处理新连接*/
if (FD_ISSET (h, &rd)) {
unsigned int l;
struct sockaddr_in client_address;
memset (&client_address, 0, l = sizeof (client_address));
r = accept (h, (struct sockaddr *)&client_address, &l);
if (r < 0) {
perror ("accept()");
} else {
/*关闭原有连接，把新连接作为fd1，同时连接新的目标fd2*/
SHUT_FD1;
SHUT_FD2;
buf1_avail = buf1_written = 0;
buf2_avail = buf2_written = 0;
fd1 = r;
fd2 = connect_socket (forward_port, argv[3]);
if (fd2 < 0) {
SHUT_FD1;
} else
printf ("connect from %s\n", inet_ntoa(client_address.sin_addr));
}
}

/* NB: read oob data before normal reads */
if (fd1 > 0)
if (FD_ISSET (fd1, &er)) {
char c;
errno = 0;
r = recv (fd1, &c, 1, MSG_OOB);
if (r < 1) {
SHUT_FD1;
} else
send (fd2, &c, 1, MSG_OOB);
}

if (fd2 > 0)
if (FD_ISSET (fd2, &er)) {
char c;
errno = 0;
r = recv (fd2, &c, 1, MSG_OOB);
if (r < 1) {
SHUT_FD1;
} else
send (fd1, &c, 1, MSG_OOB);
}

/* NB: read data from fd1 */
if (fd1 > 0)
if (FD_ISSET (fd1, &rd)) {
r = read (fd1, buf1 + buf1_avail, BUF_SIZE - buf1_avail);
if (r < 1) {
SHUT_FD1;
} else
buf1_avail += r;
}

/* NB: read data from fd2 */
if (fd2 > 0)
if (FD_ISSET (fd2, &rd)) {
r = read (fd2, buf2 + buf2_avail, BUF_SIZE - buf2_avail);
if (r < 1) {
SHUT_FD2;
} else
buf2_avail += r;
}

/* NB: write data to fd1 */
if (fd1 > 0)
if (FD_ISSET (fd1, &wr)) {
r = write (fd1, buf2 + buf2_written, buf2_avail - buf2_written);
if (r < 1) {
SHUT_FD1;
} else
buf2_written += r;
}

/* NB: write data to fd1 */
if (fd2 > 0)
if (FD_ISSET (fd2, &wr)) {
r = write (fd2, buf1 + buf1_written, buf1_avail - buf1_written);
if (r < 1) {
SHUT_FD2;
} else
buf1_written += r;
}

/* check if write data has caught read data */
if (buf1_written == buf1_avail) buf1_written = buf1_avail = 0;
if (buf2_written == buf2_avail) buf2_written = buf2_avail = 0;

/* one side has closed the connection, keep writing to the other side until empty */
if (fd1 < 0 && buf1_avail - buf1_written == 0) {
SHUT_FD2;
}
if (fd2 < 0 && buf2_avail - buf2_written == 0) {
SHUT_FD1;
}
}
return 0;
}