一、多进程程并发服务器
模型
socket();
bind();
listen();
while(1){
accept();
if(fork() == 0)
{
process();
close();
exit();
}
close();
}
二、小写转大写的设计流程
1.设计流程
服务器端：
父进程一直监听有没有客户端的连接，如果有客户端连接了，就fork()出一个子进程去处理这个连接，而父进程一直监听，一旦有一个新客户端的连接就需要fork()一个新进程。
创建socket()
给套接字命名bind
创建监听上限listen()
第二部分：
while(1){
cfd=accept(); //接收客户端的连接请求
pid=fork(); 创建子进程
if(pid==0){
//进入子进程，子进程需要完成如下事情：
1.子进程无须监听，关闭监听套接字
2.读取客户端发送过来的字母
3.完成小写转大写
4.将转换完成后的大写字母返回给客户端
}else if(pid>0){
//进入父进程
1.父进程无须与客户端建立连接，关闭连接套接字
2.父进程需要回收已经死亡的子进程
}
}
客户端：
socket() 创建套接字；
connect() 实现与服务器的通信；
read/recv、write/send9() 与服务器进行通信；
close()关闭套接字
2.注意事项
- 父进程最大文件描述个数(父进程中需要close关闭accept返回的新文件描述符) 。
- 系统内创建进程个数(与内存大小相关)。
- 父进程不能回收子进程，需要注册信号捕捉函数回收子进程，避免出现僵尸进程。
三、代码实现：小写转换大写
（1）server.c
void wait_child(int signo)
{
while (waitpid(0, NULL, WNOHANG) > 0);
//回收子进程
return ;
}
int main(void)
{
pid_t pid;
int lfd, cfd;
struct sockaddr_in serv_addr, clie_addr;
socklen_t clie_addr_len;
char buf[BUFSIZ], clie_IP[BUFSIZ];
int n, i;
lfd = Socket(AF_INET, SOCK_STREAM, 0);
bzero(&serv_addr, sizeof(serv_addr));//将地址结构清零
serv_addr.sin_family = AF_INET;
serv_addr.sin_port = htons(SERV_PORT);
serv_addr.sin_addr.s_addr = htonl(INADDR_ANY);
Bind(lfd, (struct sockaddr *)&serv_addr, sizeof(serv_addr));
Listen(lfd, 128);
while (1) {
clie_addr_len = sizeof(clie_addr);
cfd = Accept(lfd, (struct sockaddr *)&clie_addr, &clie_addr_len);
printf("client IP:%s, port:%d\n",
inet_ntop(AF_INET, &clie_addr.sin_addr.s_addr, clie_IP, sizeof(clie_IP)),
ntohs(clie_addr.sin_port));
pid = fork();//创建子进程
if (pid < 0) {
perr_exit("fork error");
//perror("fork error");
//exit(1);
} else if (pid == 0) {
close(lfd);
break;
} else {
close(cfd);
signal(SIGCHLD, wait_child);
}
}
if (pid == 0) {
//while(1)实现多次写
while (1) {
n = Read(cfd, buf, sizeof(buf));
if (n == 0) { //client close
close(cfd);
return 0;
} else if (n == -1) {
perror("read error");
exit(1);
} else {
for (i = 0; i < n; i++)
buf[i] = toupper(buf[i]);
write(cfd, buf, n);
write(STDOUT_FILENO, buf, n);//写到标准输出，方便查看
}
}
}
return 0;
}
（2）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);
（3）wrap.c
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;
}
（4）client.c
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;
}
（5）makefile
src = $(wildcard *.c)
obj = $(patsubst %.c, %.o, $(src))
all: server client
server: server.o wrap.o
gcc server.o wrap.o -o server -Wall
client: client.o wrap.o
gcc client.o wrap.o -o client -Wall
%.o:%.c
gcc -c $< -Wall
.PHONY: clean all
clean:
-rm -rf server client $(obj)
四、测试
