实现流程
1、 Socket(); 创建 监听套接字 lfd
2、 Bind() 绑定地址结构 Strcut sockaddr_in addr;
3、 Listen(); 设置监听上限
4、主业务逻辑
while (1) {
cfd = Accpet(); 接收客户端连接请求。
pid = fork();
if (pid == 0){ 子进程 read(cfd) --- 小-》大 --- write(cfd)
close(lfd) 关闭用于建立连接的套接字 lfd
read()
小--大
write()
} else if （pid > 0） {
close(cfd); 关闭用于与客户端通信的套接字 cfd
contiue;
}
}
5、子进程
close(lfd)
read()
小--大
write()
6、 父进程
close(cfd);
注册信号捕捉函数： SIGCHLD
在回调函数中， 完成子进程回收
while （waitpid()）;
测试代码
server.c
#include <stdio.h>
#include <string.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <signal.h>
#include <sys/wait.h>
#include <ctype.h>
#include <unistd.h>
#include <string.h>
#include <stdlib.h>
#include "wrap.h"
#define MAXLINE 8192
#define SERV_PORT 8000
void do_sigchild(int num)
{
while (waitpid(0, NULL, WNOHANG) > 0)
;
}
int main(void)
{
struct sockaddr_in servaddr, cliaddr;
socklen_t cliaddr_len;
int listenfd, connfd;
char buf[MAXLINE];
char str[INET_ADDRSTRLEN];//INET_ADDRSTRLEN = 16
int i, n;
pid_t pid;
struct sigaction newact;
newact.sa_handler = do_sigchild;
sigemptyset(&newact.sa_mask);
newact.sa_flags = 0;
sigaction(SIGCHLD, &newact, NULL);
listenfd = Socket(AF_INET, SOCK_STREAM, 0);
int opt = 1;
setsockopt(listenfd, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt));
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);
printf("Accepting connections ...\n");
while (1) {
cliaddr_len = sizeof(cliaddr);
connfd = Accept(listenfd, (struct sockaddr *)&cliaddr, &cliaddr_len);
printf("-------------------------%d\n", connfd);
pid = fork();
if (pid == 0) {
Close(listenfd);
while (1) {
n = Read(connfd, buf, MAXLINE);
if (n == 0) {
printf("the other side has been closed.\n");
break;
}
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]);
Write(STDOUT_FILENO, buf, n);
Write(connfd, buf, n);
}
Close(connfd);
return 0;
} else if (pid > 0) {
Close(connfd);
} else
perr_exit("fork");
}
return 0;
}
client.c
/* client.c */
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include "wrap.h"
#define MAXLINE 8192
#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");
break;
}
else
Write(STDOUT_FILENO, buf, n);
}
Close(sockfd);
return 0;
}
函数封装
wrap.h
#ifndef __WRAP_H_
#define __WRAP_H_
void perr_exit(const char *s);
int Accept(int fd, struct sockaddr *sa, socklen_t *salenptr);
int Bind(int fd, const struct sockaddr *sa, socklen_t salen);
int Connect(int fd, const struct sockaddr *sa, socklen_t salen);
int 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);
int Close(int fd);
ssize_t Readn(int fd, void *vptr, size_t n);
ssize_t Writen(int fd, const void *vptr, size_t n);
ssize_t my_read(int fd, char *ptr);
ssize_t Readline(int fd, void *vptr, size_t maxlen);
#endif
wrap.c
#include <stdlib.h>
#include <stdio.h>
#include <unistd.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;
}
int Bind(int fd, const struct sockaddr *sa, socklen_t salen)
{
int n;
if ((n = bind(fd, sa, salen)) < 0)
perr_exit("bind error");
return n;
}
int Connect(int fd, const struct sockaddr *sa, socklen_t salen)
{
int n;
if ((n = connect(fd, sa, salen)) < 0)
perr_exit("connect error");
return n;
}
int Listen(int fd, int backlog)
{
int n;
if ((n = listen(fd, backlog)) < 0)
perr_exit("listen error");
return n;
}
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;
}
int Close(int fd)
{
int n;
if ((n = close(fd)) == -1)
perr_exit("close error");
return n;
}
/*参三: 应该读取的字节数*/
ssize_t Readn(int fd, void *vptr, size_t n)
{
size_t nleft; //usigned int 剩余未读取的字节数
ssize_t nread; //int 实际读到的字节数
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;
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;
}
测试结果
关闭后
