Linux：TCP/UDP实现服务器+客户端

程序员文章站 2022-06-06 08:44:20

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编译环境：Linux 10.04 LTS GCC

TCP协议：

服务器：

/* server.c */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include "wrap.h"

#define MAXLINE 80
#define SERV_PORT 8000

int main(int argc, char **argv)
{
	int i, maxi, maxfd, listenfd, connfd, sockfd;
	int nready, client[FD_SETSIZE];
	ssize_t n;
	fd_set rset, allset;
	char buf[MAXLINE];
	char str[INET_ADDRSTRLEN];
	socklen_t cliaddr_len;
	struct sockaddr_in	cliaddr, servaddr;

	listenfd = Socket(AF_INET, SOCK_STREAM, 0);

	bzero(&servaddr, sizeof(servaddr));
	servaddr.sin_family      = AF_INET;
	servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
	servaddr.sin_port        = htons(SERV_PORT);

	Bind(listenfd, (struct sockaddr *)&servaddr, sizeof(servaddr));

	Listen(listenfd, 20);

	maxfd = listenfd;		/* initialize */
	maxi = -1;			/* index into client[] array */
	for (i = 0; i < FD_SETSIZE; i++)
		client[i] = -1;	/* -1 indicates available entry */
	FD_ZERO(&allset);
	FD_SET(listenfd, &allset);

	for ( ; ; ) 
	{
		rset = allset;	/* structure assignment */
		nready = select(maxfd+1, &rset, NULL, NULL, NULL);
		if (nready < 0)
			perr_exit("select error");

		if (FD_ISSET(listenfd, &rset)) 
		{ /* new client connection */
			cliaddr_len = sizeof(cliaddr);
			connfd = Accept(listenfd, (struct sockaddr *)&cliaddr, &cliaddr_len);

			printf("received from %s at PORT %d\n",
			       inet_ntop(AF_INET, &cliaddr.sin_addr, str, sizeof(str)),
			       ntohs(cliaddr.sin_port));

			for (i = 0; i < FD_SETSIZE; i++)
			{
				if (client[i] < 0) 
				{
					client[i] = connfd; /* save descriptor */
					break;
				}
			}
			if (i == FD_SETSIZE) {
				fputs("too many clients\n", stderr);
				exit(1);
			}

			FD_SET(connfd, &allset);	/* add new descriptor to set */
			if (connfd > maxfd)
				maxfd = connfd; /* for select */
			if (i > maxi)
				maxi = i;	/* max index in client[] array */

			if (--nready == 0)
				continue;	/* no more readable descriptors */
		}

		for (i = 0; i <= maxi; i++) 
		{	/* check all clients for data */
			if ( (sockfd = client[i]) < 0)
				continue;
			if (FD_ISSET(sockfd, &rset)) 
			{
				if ( (n = Read(sockfd, buf, MAXLINE)) == 0) 
				{
					/* connection closed by client */
					Close(sockfd);
					FD_CLR(sockfd, &allset);
					client[i] = -1;
				} else 
				{
					int j;
					for (j = 0; j < n; j++)
						buf[j] = toupper(buf[j]);
					Write(sockfd, buf, n);
				}

				if (--nready == 0)
					break;	/* no more readable descriptors */
			}
		}
	}
}

客户端：

/* client.c */
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <netinet/in.h>
#include "wrap.h"

#define MAXLINE 80
#define SERV_PORT 8000

int main(int argc, char *argv[])
{
	struct sockaddr_in servaddr;
	char buf[MAXLINE];
	int sockfd, n;
    
	sockfd = Socket(AF_INET, SOCK_STREAM, 0);

	bzero(&servaddr, sizeof(servaddr));
	servaddr.sin_family = AF_INET;
	inet_pton(AF_INET, "127.0.0.1", &servaddr.sin_addr);
	servaddr.sin_port = htons(SERV_PORT);
    
	Connect(sockfd, (struct sockaddr *)&servaddr, sizeof(servaddr));

	while (fgets(buf, MAXLINE, stdin) != NULL)
	{
		Write(sockfd, buf, strlen(buf));
		n = Read(sockfd, buf, MAXLINE);
		if (n == 0)
			printf("the other side has been closed.\n");
		else
			Write(STDOUT_FILENO, buf, n);
	}

	Close(sockfd);
	return 0;
}

wrap.h

void perr_exit(const char *s);

int Accept(int fd, struct sockaddr *sa, socklen_t *salenptr);

void Bind(int fd, const struct sockaddr *sa, socklen_t salen);

void Connect(int fd, const struct sockaddr *sa, socklen_t salen);


void Listen(int fd, int backlog);


int Socket(int family, int type, int protocol);


ssize_t Read(int fd, void *ptr, size_t nbytes);

ssize_t Write(int fd, const void *ptr, size_t nbytes);


void Close(int fd);

ssize_t Readn(int fd, void *vptr, size_t n);


ssize_t Writen(int fd, const void *vptr, size_t n);


static ssize_t my_read(int fd, char *ptr);


ssize_t Readline(int fd, void *vptr, size_t maxlen);

wrap.c

#include <stdlib.h>
#include <errno.h>
#include <sys/socket.h>

void perr_exit(const char *s)
{
	perror(s);
	exit(1);
}

int Accept(int fd, struct sockaddr *sa, socklen_t *salenptr)
{
	int n;

again:
	if ( (n = accept(fd, sa, salenptr)) < 0)
	{
		if ((errno == ECONNABORTED) || (errno == EINTR))
			goto again;
		else
			perr_exit("accept error");
	}
	return n;
}

void Bind(int fd, const struct sockaddr *sa, socklen_t salen)
{
	if (bind(fd, sa, salen) < 0)
		perr_exit("bind error");
}

void Connect(int fd, const struct sockaddr *sa, socklen_t salen)
{
	if (connect(fd, sa, salen) < 0)
		perr_exit("connect error");
}

void Listen(int fd, int backlog)
{
	if (listen(fd, backlog) < 0)
		perr_exit("listen error");
}

int Socket(int family, int type, int protocol)
{
	int n;

	if ( (n = socket(family, type, protocol)) < 0)
		perr_exit("socket error");
	return n;
}

ssize_t Read(int fd, void *ptr, size_t nbytes)
{
	ssize_t n;

again:
	if ( (n = read(fd, ptr, nbytes)) == -1)
	{
		if (errno == EINTR)
			goto again;
		else
			return -1;
	}
	return n;
}

ssize_t Write(int fd, const void *ptr, size_t nbytes)
{
	ssize_t n;

again:
	if ( (n = write(fd, ptr, nbytes)) == -1) {
		if (errno == EINTR)
			goto again;
		else
			return -1;
	}
	return n;
}

void Close(int fd)
{
	if (close(fd) == -1)
		perr_exit("close error");
}

ssize_t Readn(int fd, void *vptr, size_t n)
{
	size_t  nleft;
	ssize_t nread;
	char   *ptr;

	ptr = vptr;
	nleft = n;
	while (nleft > 0)
	{
		if ( (nread = read(fd, ptr, nleft)) < 0)
		{		
			if (errno == EINTR)
				nread = 0;
			else
				return -1;
		} else if (nread == 0)
			break;

		nleft -= nread;
		ptr += nread;
	}
	return n - nleft;
}

ssize_t Writen(int fd, const void *vptr, size_t n)
{
	size_t nleft;
	ssize_t nwritten;
	const char *ptr;

	ptr = vptr;
	nleft = n;
	while (nleft > 0) {
		if ( (nwritten = write(fd, ptr, nleft)) <= 0) {
			if (nwritten < 0 && errno == EINTR)
				nwritten = 0;
			else
				return -1;
		}

		nleft -= nwritten;
		ptr += nwritten;
	}
	return n;
}

static ssize_t my_read(int fd, char *ptr)
{
	static int read_cnt = 0;
	static char *read_ptr;
	static char read_buf[100];

	if (read_cnt <= 0)
	{
	again:
		if ( (read_cnt = read(fd, read_buf, sizeof(read_buf))) < 0)
		{
			if (errno == EINTR)
			{
				goto again;
			}
			return -1;
		}
		else if (read_cnt == 0)
		{
			return 0;
		}
		read_ptr = read_buf;
	}
	read_cnt--;
	*ptr = *read_ptr++;
	return 1;
}

ssize_t Readline(int fd, void *vptr, size_t maxlen)
{
	ssize_t n, rc;
	char    c, *ptr;

	ptr = vptr;
	for (n = 1; n < maxlen; n++)
	{
		if ( (rc = my_read(fd, &c)) == 1)
	  {
			*ptr++ = c;
			if (c  == '\n')
				break;
		} else if (rc == 0)
	  {
			*ptr = 0;
			return n - 1;
		} else
			return -1;
	}
	*ptr  = 0;
	return n;
}

UDP协议：

服务器：

/* server.c */
#include <stdio.h>
#include <string.h>
#include <netinet/in.h>
#include "wrap.h"

#define MAXLINE 80
#define SERV_PORT 8000

int main(void)
{
	struct sockaddr_in servaddr, cliaddr;
	socklen_t cliaddr_len;
	int sockfd;
	char buf[MAXLINE];
	char str[INET_ADDRSTRLEN];
	int i, n;

	sockfd = Socket(AF_INET, SOCK_DGRAM, 0);

	bzero(&servaddr, sizeof(servaddr));
	servaddr.sin_family = AF_INET;
	servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
	servaddr.sin_port = htons(SERV_PORT);
    
	Bind(sockfd, (struct sockaddr *)&servaddr, sizeof(servaddr));

	printf("Accepting connections ...\n");
	while (1) {
		cliaddr_len = sizeof(cliaddr);
		n = recvfrom(sockfd, buf, MAXLINE, 0, (struct sockaddr *)&cliaddr, &cliaddr_len);
		if (n == -1)
			perr_exit("recvfrom error");
		printf("received from %s at PORT %d\n",
		       inet_ntop(AF_INET, &cliaddr.sin_addr, str, sizeof(str)),
		       ntohs(cliaddr.sin_port));
    
		for (i = 0; i < n; i++)
			buf[i] = toupper(buf[i]);
		n = sendto(sockfd, buf, n, 0, (struct sockaddr *)&cliaddr, sizeof(cliaddr));
		if (n == -1)
			perr_exit("sendto error");
	}
}

客户端：

/* client.c */
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <netinet/in.h>
#include "wrap.h"

#define MAXLINE 80
#define SERV_PORT 8000

int main(int argc, char *argv[])
{
	struct sockaddr_in servaddr;
	int sockfd, n;
	char buf[MAXLINE];
	char str[INET_ADDRSTRLEN];
	socklen_t servaddr_len;
    
	sockfd = Socket(AF_INET, SOCK_DGRAM, 0);

	bzero(&servaddr, sizeof(servaddr));
	servaddr.sin_family = AF_INET;
	inet_pton(AF_INET, "127.0.0.1", &servaddr.sin_addr);
	servaddr.sin_port = htons(SERV_PORT);
    
	while (fgets(buf, MAXLINE, stdin) != NULL) {
		n = sendto(sockfd, buf, strlen(buf), 0, (struct sockaddr *)&servaddr, sizeof(servaddr));
		if (n == -1)
			perr_exit("sendto error");

		n = recvfrom(sockfd, buf, MAXLINE, 0, NULL, 0);
		if (n == -1)
			perr_exit("recvfrom error");
	  
		Write(STDOUT_FILENO, buf, n);
	}

	Close(sockfd);
	return 0;
}

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