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linux系统编程09-进程间通信

news 2025/9/17 0:14:50

目录
  • 介绍
  • 1. 管道
    • 匿名管道
    • 命名管道
  • 2. IPC：XSI → SysV
    • Message Queues
    • Semaphore Arrays
    • Shared Memory
  • 3. 网络套接字socket
    • udp
      • 单播
      • 广播
      • 多播
    • tcp
      • 单进程
      • 多进程
      • pool_static：静态进程池
      • pool_dynamic：动态进程池

介绍

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1. 管道

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  • 命名管道就是一块磁盘上的文件，不同进程通过读写该文件进行通信
  • 匿名管道同样是在磁盘上创建了文件，但是只返回文件描述符，其他进程看不到，所以只能用于有亲缘关系的进程

匿名管道

  • 管道是阻塞的：有写者的时候，读者会阻塞读
##include <unistd.h>
int pipe(int pipefd[2]);
  • 参数： pid 文件描述符数组， pid[0] 读端， pid[1] 写端
  • 返回值： <0 失败

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例子：pipe实现父子进程间通信

示例代码：

##include<stdio.h>
##include<stdlib.h>
##include<unistd.h>
##include<sys/wait.h>##define BUFSIZE 1024int main()
{size_t pid;int pd[2];int len;char buf[BUFSIZE];if(pipe(pd)<0){perror("pipe()");exit(1);}pid = fork();if(pid < 0){perror("fork()");exit(1);}if(pid == 0)  //child read{close(pd[1]);len = read(pd[0],buf,BUFSIZE);write(1,buf,len);close(pd[0]);exit(0);}else        //parent write{close(pd[0]);write(pd[1], "Hello", 6);close(pd[1]);wait(NULL);exit(0);}
}

运行结果：

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项目相关：

父进程做好管道，子进程 exec 变成播放器，然后父子进程通过管道通信

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mpg123 [ options ] file-or-URL...or -

sudo apt install mpg123 → man mpg123

mpg123 歌曲名 ：播放歌曲， ‘-’表示从标准输入读取内容播放

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##include<stdio.h>
##include<stdlib.h>
##include<unistd.h>
##include<sys/wait.h>##define BUFSIZE 1024int main()
{size_t pid;int pd[2];int len;char buf[BUFSIZE];if(pipe(pd)<0){perror("pipe()");exit(1);}pid = fork();if(pid < 0){perror("fork()");exit(1);}if(pid == 0)  //child read{close(pd[1]); //关闭写d端dup2(pd[0],0); //重定向读端到标准输入close(pd[0]);fd = open("/dev/null",O_RDWR);dup2(fd,1);dup2(fd,2);execl("/usr/bin/mpg123", "mpg123", "-", NULL);perror("execl()");exit(1);}else        //parent write{close(pd[0]); //关闭读端//父进程从网上收数据，往管道中x写close(pd[1]);wait(NULL);exit(0);}
}
ub

命名管道

mkfifo 命令：创建管道文件

阻塞：没凑齐读写双方时会阻塞

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2. IPC：XSI → SysV

ipcs 命令：展现机制

key : ftok()

Message Queues ：xxxget() xxxop()[包括cv和snd] xxxctl()

Semaphore Arrays

Shared Memory

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常规的操作流程：

  1. 创建实例： ftok() xxxget()
  2. 操作： xxxop()
  3. 删除实例： xxxctl()

Message Queues

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示例：消息队列实现非亲缘关系进程间通信

示例代码：

proto.h

##ifndef PROTO_H__
##define PROTO_H__##define KEYPATH     "/etc/services"
##define KEYPROJ     'g'##define NAMESIZE    32struct msg_st
{long mtype; //msgrcv中对传输数据包规定要加char name[NAMESIZE];int math;int chinese;
};##endif

snder.c

##include<stdio.h>
##include<stdlib.h>
##include<sys/types.h>
##include<sys/ipc.h>
##include<sys/msg.h>
##include<string.h>##include"proto.h"int main()
{key_t key;int msgid;struct msg_st sbuf;key = ftok(KEYPATH,KEYPROJ);if(key < 0){perror("ftok()");exit(1);}//后运行的一方只需要拿到对应的msgid即可msgid = msgget(key,0);if(msgid < 0){perror("msgget()");exit(1);}sbuf.mtype = 1;strcpy(sbuf.name, "Alan");sbuf.math = rand()%100;sbuf.chinese = rand()%100;if(msgsnd(msgid,&sbuf, sizeof(sbuf)-sizeof(long), 0) < 0){perror("msgsnd()");exit(1);}puts("ok");//没创建，所以不用销毁：msgctl();exit(0);
}

rcver.h

##include<stdio.h>
##include<stdlib.h>
##include <sys/types.h>
##include <sys/ipc.h>
##include <sys/msg.h>
##include"proto.h"int main()
{key_t key;int msgid;struct msg_st rbuf;key = ftok(KEYPATH,KEYPROJ);if(key < 0){perror("ftok()");exit(1);}//主动方：创建，让机制运行起来msgid = msgget(key, IPC_CREAT|0600);if(msgid < 0){perror("msgget()");exit(1);}while(1){if(msgrcv(msgid,&rbuf,sizeof(rbuf)-sizeof(long),0,0) < 0){perror("msgce()");exit(1);}printf("NAME = %s\n",rbuf.name);printf("MATH = %d\n",rbuf.math);printf("CHINESE = %d\n",rbuf.chinese);}msgctl(msgid, IPC_RMID, NULL);exit(0);
}

运行结果：

运行 ./rcver 后的结果

运行 ./rcver 后的结果

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注意点：

  1. 即使先发送，后接收，也能收到之前发送的内容，说明msg有缓冲机制，缓冲区的大小可以通过 ulimit -a 查看

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  2. 程序是异常终止，msg没有被销毁，如何解决

    1. 程序中加入信号和信号处理函数，在信号处理函数中关闭msg
    2. ipcrm -q msgid 如 ipcrm -q 0

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例子2：实现ftp

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状态机编程

状态机编程

协议数据设计：

方式1:

##ifndef PROTO_H__
##define PROTO_H__##define KEYPATH     "/etc/services"
##define KEYPROJ     'a'##define PATHMAX     1024
##define DATAMAX     1024enum
{MSG_PATH=1,MSG_DATA,MSG_EOT
};//S端收到一种包
typedef struct msg_path_st
{long mtype;         //must be MSG_PATHchar path[PATHMAX]; //ASCIIZ带尾0的串
}msg_path_t;//C端收到两种包
typedef struct msg_data_st
{long mtype;         //must be MSG_DATAchar data[DATAMAX];int datalen;
}msg_data_t;typedef struct msg_eot_st
{long mtype;         //must be MSG_EOT
}msg_eot_t;//用union将两个包综合
//long mytpe实际不存在，用来提取公因子，方便判断类型
union msg_s2c_un
{long mtype;msg_data_t datamsg;msg_eot_t eotmsg;
}##endif

方式2:

##ifndef PROTO_H__
##define PROTO_H__##define KEYPATH     "/etc/services"
##define KEYPROJ     'a'##define PATHMAX     1024
##define DATAMAX     1024enum
{MSG_PATH=1,MSG_DATA,MSG_EOT
};//S端收到一种包
typedef struct msg_path_st
{long mtype;         //must be MSG_PATHchar path[PATHMAX]; //ASCIIZ带尾0的串
}msg_path_t;//C端收到两种包，合并为一种结构体
//没第一种做法好，只适用于eot中只用mtype的情况
typedef struct msg_s2c_st
{long mtype;         //must be MSG_DATA or MSG_EOTchar data[DATAMAX];int datalen;/** datalen > 0 :data*         < 0 :eot*/
}msg_s2c_t;##endif

Semaphore Arrays

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信号量数组的必要性：

  1. 银行家算法中，AB两个信号量要同时被分配，防止死锁
  2. 两个进程逆序申请两个锁的时候，操作要是原子的
  3. 本质就是把几个信号量的操作原子化

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例子：重构 lockf，二十个进程同步往 /tmp/out 加1

示例代码：

##include<stdio.h>
##include<stdlib.h>
##include<string.h>
##include<wait.h>
##include<unistd.h>
##include<sys/types.h>
##include<sys/ipc.h>
##include<sys/sem.h>
##include<errno.h>##define PROCNUM     20
##define FILENAME    "/tmp/out"
##define LINESIZE     1024int semid;static void P(void)
{struct sembuf op[1];op[0].sem_num = 0;op[0].sem_op = -1;op[0].sem_flg = 0;while(semop(semid,op,1) < 0){if(errno != EINTR || errno != EAGAIN){perror("semop()");exit(1);}}
}static void V(void)
{struct sembuf op[1];op[0].sem_num = 0;op[0].sem_op = 1;op[0].sem_flg = 0;if(semop(semid,op,1)<0){perror("semop()");exit(1);}
}static void func_add(void)
{FILE *fp;int fd;char linebuf[LINESIZE];fp = fopen(FILENAME, "r+");if(fp == NULL){perror("fopen()");exit(1);}P();fgets(linebuf, LINESIZE, fp);fseek(fp, 0, SEEK_SET);//sleep(1);fprintf(fp, "%d\n",atoi(linebuf)+1);fflush(fp); //文件全缓冲V();fclose(fp);
}int main()
{int i,err;size_t pid;//key_t key;//key = ftok();//1.创建:由于父子进程共享semid//所以不需要用key生成。1为数组元素semid = semget(IPC_PRIVATE,1,0600);if(semid<0){perror("semget()");exit(1);}//2.初始化:设置下标为0的元素值为1if(semctl(semid,0,SETVAL,1) < 0){perror("semctl");exit(1);}for(i = 0; i < PROCNUM; i++){pid = fork();if(pid < 0){perror("fork()");exit(1);}if(pid == 0){func_add();exit(0);}}for(i = 0; i < PROCNUM; i++)wait(NULL);//3.移除:既然要销毁，0不当下标了semctl(semid,0,IPC_RMID);exit(0);
}

运行结果：

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Shared Memory

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例子：父子进程通信，子写父读

示例代码：

##include<stdio.h>
##include<stdlib.h>
##include<unistd.h>
##include<sys/types.h>
##include<sys/ipc.h>
##include<sys/shm.h>
##include<sys/wait.h>
##include<string.h>##define MEMSIZE 1024
int main()
{pid_t pid;int shmid;char *ptr;//ftok(); 有亲缘关系，不需要shmid = shmget(IPC_PRIVATE,MEMSIZE ,0600);if(shmid < 0){perror("shmif()");exit(1);}pid = fork();if(pid < 0){perror("fork()");exit(1);}if(pid == 0)  //child write{ptr = shmat(shmid,NULL,0);if(ptr == (void*)-1){perror("shmat()");exit(1);}strcpy(ptr, "Hello World");shmdt(ptr); //解除映射exit(0);}else          //parent read{wait(NULL);ptr = shmat(shmid, NULL,0);if(ptr == (void*)-1){perror("shmat()");exit(1);}puts(ptr);shmdt(ptr);shmctl(shmid, IPC_RMID, NULL); //销毁实例exit(0);}exit(0);
}

运行结果：

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3. 网络套接字socket

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socket是什么：向下给各层数据传输协议，向上给两种传输方式（数据报、流式）封装出的接口

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使用 socket 的方式

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用domain协议族里的协议protocol，实现type类型的传输。返回的是文件描述符，当文件来操作。

udp

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struct sockadd 实际上不存在，需要 man 7 ip 查看 socket format 得到对应的结构体

单播

例子1：基本使用

示例代码：

  • proto.h【规定数据报格式】

    #ifndef PROTO_H__
#define PROTO_H__#define RCVPORT "1989"   //封装端口(最好>1024)#define NAMESIZE    11struct msg_st
{uint8_t name[NAMESIZE];uint32_t math;uint32_t chinese;
}__attribute__((packed)); //告诉编译器不对齐#endif

  • recver.c

    #include<stdio.h>
#include<stdlib.h>
#include<sys/types.h>
#include<sys/socket.h>
#include<arpa/inet.h>
#include<unistd.h>#include"proto.h"#define IPSTRSIZE 20int main()
{int sd;struct sockaddr_in localaddr, remoteaddr; //具体是什么结构体取决于协议//看手册 man 7 xx(proto) 里的 Address_formatstruct msg_st rbuf;socklen_t remoteaddr_len;char ipstr[IPSTRSIZE];//创建socketsd = socket(AF_INET,SOCK_DGRAM,0/*IPPROTO_UDP*/);//0表示默认协议if(sd < 0){perror("socket()");exit(1);}localaddr.sin_family = AF_INET;localaddr.sin_port = htons(atoi(RCVPORT));inet_pton(AF_INET,"0.0.0.0",&localaddr.sin_addr); //0.0.0.0在绑定阶段会绑定自身ip//取得地址if(bind(sd,(void*)&localaddr,sizeof(localaddr)) < 0) //void *百搭{perror("bind()");exit(1);}/*!!!!*/remoteaddr_len = sizeof(remoteaddr);while(1){recvfrom(sd,&rbuf,sizeof(rbuf),0,(void*)&remoteaddr,&remoteaddr_len);inet_ntop(AF_INET, &remoteaddr.sin_addr, ipstr, IPSTRSIZE);printf("----MESSAGE FROM %s:%d------\n", ipstr, ntohs(remoteaddr.sin_port));printf("NAME = %s\n",rbuf.name);printf("MATH = %d\n",ntohl(rbuf.math));printf("CHINESE = %d\n",ntohl(rbuf.chinese));}close(sd);exit(0);
}

  • snder.c

    #include<stdio.h>
#include<stdlib.h>
#include<sys/types.h>
#include<sys/socket.h>
#include<arpa/inet.h>
#include<string.h>
#include<unistd.h>#include"proto.h"int main(int argc, char **argv) //传ip地址
{if(argc < 2){fprintf(stderr, "Usage:...\n");exit(1);}int sd;struct msg_st sbuf;struct sockaddr_in raddr;sd = socket(AF_INET,SOCK_DGRAM,0);if(sd < 0){perror("socket()");exit(1);}//bind();strcpy(sbuf.name, "Alan");sbuf.math = htonl(rand()%100);sbuf.chinese = htonl(rand()%100);raddr.sin_family = AF_INET;raddr.sin_port = htons(atoi(RCVPORT));inet_pton(AF_INET, argv[1], &raddr.sin_addr);if(sendto(sd,&sbuf, sizeof(sbuf), 0, (void*)&raddr, sizeof(raddr)) < 0){perror("sendto()");exit(1);}puts("OK");close(sd);exit(0);
}

运行结果：

运行recver.c后，执行 **** 查看udp套接字使用情况

运行recver.c后，执行 netstat -anu 查看udp套接字使用情况

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发送端没有bind端口任意指定

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例子二：发送变长数组

思路： proto改变变长数组，发送的时候malloc申请内存，接收的时候按最大空间接收

示例代码：

  • proto.h

    #ifndef PROTO_H__
#define PROTO_H__#define RCVPORT "1989"   //封装端口(最好>1024)#define NAMEMAX    (512-8-8)struct msg_st
{uint32_t math;uint32_t chinese;uint8_t name[1]; //变长数组
}__attribute__((packed)); //告诉编译器不对齐#endif

  • snder.c

    #include<stdio.h>
#include<stdlib.h>
#include<sys/types.h>
#include<sys/socket.h>
#include<arpa/inet.h>
#include<string.h>
#include<unistd.h>#include"proto.h"int main(int argc, char **argv) //传ip地址
{if(argc < 3){fprintf(stderr, "Usage:...\n");exit(1);}int sd;int size;struct msg_st *sbufp;struct sockaddr_in raddr;size = sizeof(struct msg_st)+strlen(argv[2]);sbufp = malloc(size);if(sbufp == NULL){perror("malloc()");exit(1);}sd = socket(AF_INET,SOCK_DGRAM,0);if(sd < 0){perror("socket()");exit(1);}//bind();if(strlen(argv[2]) > NAMEMAX){fprintf(stderr, "NAME is too long\n");exit(1);}strcpy(sbufp->name, argv[2]);sbufp->math = htonl(rand()%100);sbufp->chinese = htonl(rand()%100);raddr.sin_family = AF_INET;raddr.sin_port = htons(atoi(RCVPORT));inet_pton(AF_INET, argv[1], &raddr.sin_addr);if(sendto(sd,sbufp, size, 0, (void*)&raddr, sizeof(raddr)) < 0){perror("sendto()");exit(1);}puts("OK");close(sd);free(sbufp);exit(0);
}

  • recver.c

    #include<stdio.h>
#include<stdlib.h>
#include<sys/types.h>
#include<sys/socket.h>
#include<arpa/inet.h>
#include<unistd.h>#include"proto.h"#define IPSTRSIZE 20int main()
{int sd;int size;struct sockaddr_in localaddr, remoteaddr; //具体是什么结构体取决于协议//看手册 man 7 xx(proto) 里的 Address_formatstruct msg_st *rbufp;socklen_t remoteaddr_len;char ipstr[IPSTRSIZE];sd = socket(AF_INET,SOCK_DGRAM,0/*IPPROTO_UDP*/);//0表示默认协议if(sd < 0){perror("socket()");exit(1);}size = sizeof(struct msg_st) + NAMEMAX - 1;rbufp = malloc(size);if(rbufp == NULL){perror("malloc()");exit(1);}localaddr.sin_family = AF_INET;localaddr.sin_port = htons(atoi(RCVPORT));inet_pton(AF_INET,"0.0.0.0",&localaddr.sin_addr); //0.0.0.0在绑定阶段会绑定自身ipif(bind(sd,(void*)&localaddr,sizeof(localaddr)) < 0) //void *百搭{perror("bind()");exit(1);}/*!!!!*/remoteaddr_len = sizeof(remoteaddr);while(1){recvfrom(sd,rbufp,size,0,(void*)&remoteaddr,&remoteaddr_len);inet_ntop(AF_INET, &remoteaddr.sin_addr, ipstr, IPSTRSIZE);printf("----MESSAGE FROM %s:%d------\n", ipstr, ntohs(remoteaddr.sin_port));printf("NAME = %s\n",rbufp->name);printf("MATH = %d\n",ntohl(rbufp->math));printf("CHINESE = %d\n",ntohl(rbufp->chinese));}close(sd);exit(0);
}

运行结果：

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广播

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多播与广播需要设置：用到函数 setsockopt

int setsockopt(int sockfd, int level, int optname,const void *optval, socklen_t optlen);

这个函数横跨ip，tcp，udp， level 指定协议， optname 是具体设置的项目， optval 是参数， optlen 是参数的sizeof。

level 和 optname 从哪里获取？ man 7 ip/tcp/udp 查看 Socket Option 即可。

比如 man 7 udp 查看 socket Option，可知， level == SOL_SOCKET，打开广播的选项 opt == SO_BROADCAST

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示例代码：

  • snder.c

    #include<stdio.h>
#include<stdlib.h>
#include<sys/types.h>
#include<sys/socket.h>
#include<arpa/inet.h>
#include<string.h>
#include<unistd.h>#include"proto.h"int main(int argc, char **argv) //传ip地址
{int sd;struct msg_st sbuf;struct sockaddr_in raddr;sd = socket(AF_INET,SOCK_DGRAM,0);if(sd < 0){perror("socket()");exit(1);}//打开广播选项int val = 1;if(setsockopt(sd,SOL_SOCKET,SO_BROADCAST,&val,sizeof(val)) < 0){perror("setsockopt()");exit(1);}strcpy(sbuf.name, "Alan");sbuf.math = htonl(rand()%100);sbuf.chinese = htonl(rand()%100);raddr.sin_family = AF_INET;raddr.sin_port = htons(atoi(RCVPORT));inet_pton(AF_INET, "255.255.255.255", &raddr.sin_addr); //全网广播if(sendto(sd,&sbuf, sizeof(sbuf), 0, (void*)&raddr, sizeof(raddr)) < 0){perror("sendto()");exit(1);}puts("OK");close(sd);exit(0);
}

  • recver.c

    #include<stdio.h>
#include<stdlib.h>
#include<sys/types.h>
#include<sys/socket.h>
#include<arpa/inet.h>
#include<unistd.h>#include"proto.h"#define IPSTRSIZE 20int main()
{int sd;struct sockaddr_in localaddr, remoteaddr; //具体是什么结构体取决于协议//看手册 man 7 xx(proto) 里的 Address_formatstruct msg_st rbuf;socklen_t remoteaddr_len;char ipstr[IPSTRSIZE];sd = socket(AF_INET,SOCK_DGRAM,0/*IPPROTO_UDP*/);//0表示默认协议if(sd < 0){perror("socket()");exit(1);}int val = 1;if(setsockopt(sd,SOL_SOCKET,SO_BROADCAST,&val,sizeof(val)) < 0){perror("setsockopt()");exit(1);}localaddr.sin_family = AF_INET;localaddr.sin_port = htons(atoi(RCVPORT));inet_pton(AF_INET,"0.0.0.0",&localaddr.sin_addr); //0.0.0.0在绑定阶段会绑定自身ipif(bind(sd,(void*)&localaddr,sizeof(localaddr)) < 0) //void *百搭{perror("bind()");exit(1);}/*!!!!*/remoteaddr_len = sizeof(remoteaddr);while(1){recvfrom(sd,&rbuf,sizeof(rbuf),0,(void*)&remoteaddr,&remoteaddr_len);inet_ntop(AF_INET, &remoteaddr.sin_addr, ipstr, IPSTRSIZE);printf("----MESSAGE FROM %s:%d------\n", ipstr, ntohs(remoteaddr.sin_port));printf("NAME = %s\n",rbuf.name);printf("MATH = %d\n",ntohl(rbuf.math));printf("CHINESE = %d\n",ntohl(rbuf.chinese));}close(sd);exit(0);
}

运行结果：

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多播

实现在ip层， man 7 ip → Socket Option

发送方建立多播组，接受方如果要接受该多播组，就加入，所以协议（proto.h）中要加入多播组的字段

示例代码：

  • proto.h

    #ifndef PROTO_H__
#define PROTO_H__#define MTROUP  "224.2.2.2" //多播:D类地址
#define RCVPORT "1989"   //封装端口(最好>1024)#define NAMESIZE    11struct msg_st
{uint8_t name[NAMESIZE];uint32_t math;uint32_t chinese;
}__attribute__((packed)); //告诉编译器不对齐#endif

  • snder.c

    #include<stdio.h>
#include<stdlib.h>
#include<sys/types.h>
#include<sys/socket.h>
#include<arpa/inet.h>
#include<string.h>
#include<unistd.h>
#include<net/if.h>#include"proto.h"int main(int argc, char **argv) //传ip地址
{int sd;struct msg_st sbuf;struct sockaddr_in raddr;sd = socket(AF_INET,SOCK_DGRAM,0);if(sd < 0){perror("socket()");exit(1);}//打开广播选项struct ip_mreqn mreq;inet_pton(AF_INET,MTROUP,&mreq.imr_multiaddr);inet_pton(AF_INET,"0.0.0.0",&mreq.imr_address);mreq.imr_ifindex = if_nametoindex("eth0");//网络设备名转网络索引号if(setsockopt(sd,IPPROTO_IP,IP_MULTICAST_IF,&mreq,sizeof(mreq)) < 0){perror("setsockopt()");exit(1);}strcpy(sbuf.name, "Alan");sbuf.math = htonl(rand()%100);sbuf.chinese = htonl(rand()%100);raddr.sin_family = AF_INET;raddr.sin_port = htons(atoi(RCVPORT));inet_pton(AF_INET, MTROUP, &raddr.sin_addr); //全网广播if(sendto(sd,&sbuf, sizeof(sbuf), 0, (void*)&raddr, sizeof(raddr)) < 0){perror("sendto()");exit(1);}puts("OK");close(sd);exit(0);
}

  • recver.c

    #include<stdio.h>
#include<stdlib.h>
#include<sys/types.h>
#include<sys/socket.h>
#include<arpa/inet.h>
#include<unistd.h>
#include<net/if.h>#include"proto.h"#define IPSTRSIZE 20int main()
{int sd;struct sockaddr_in localaddr, remoteaddr; //具体是什么结构体取决于协议//看手册 man 7 xx(proto) 里的 Address_formatstruct msg_st rbuf;socklen_t remoteaddr_len;char ipstr[IPSTRSIZE];sd = socket(AF_INET,SOCK_DGRAM,0/*IPPROTO_UDP*/);//0表示默认协议if(sd < 0){perror("socket()");exit(1);}//加入多播组struct ip_mreqn mreq;inet_pton(AF_INET,MTROUP,&mreq.imr_multiaddr);inet_pton(AF_INET,"0.0.0.0",&mreq.imr_address);mreq.imr_ifindex = if_nametoindex("eth0");if(setsockopt(sd,IPPROTO_IP,IP_ADD_MEMBERSHIP,&mreq, sizeof(mreq)) < 0){perror("setsockopt()");exit(1);}localaddr.sin_family = AF_INET;localaddr.sin_port = htons(atoi(RCVPORT));inet_pton(AF_INET,"0.0.0.0",&localaddr.sin_addr); //0.0.0.0在绑定阶段会绑定自身ipif(bind(sd,(void*)&localaddr,sizeof(localaddr)) < 0) //void *百搭{perror("bind()");exit(1);}/*!!!!*/remoteaddr_len = sizeof(remoteaddr);while(1){recvfrom(sd,&rbuf,sizeof(rbuf),0,(void*)&remoteaddr,&remoteaddr_len);inet_ntop(AF_INET, &remoteaddr.sin_addr, ipstr, IPSTRSIZE);printf("----MESSAGE FROM %s:%d------\n", ipstr, ntohs(remoteaddr.sin_port));printf("NAME = %s\n",rbuf.name);printf("MATH = %d\n",ntohl(rbuf.math));printf("CHINESE = %d\n",ntohl(rbuf.chinese));}close(sd);exit(0);
}

运行结果：

Untitled

查看网络设备名称和编号 ip ad sh ：

Untitled

注意： 224.0.0.1 所有支持多播的结点，都默认在这个组中，且无法离开，相当于 255.255.255.255 （广播）

tcp

Untitled

struct sockadd 实际上不存在，需要 man 7 ip 查看 socket format 得到对应的结构体

单进程

示例代码：

  • proto.h

    #ifndef PROTO_H__
#define PROTO_H__#define SERVERPORT "1989"#define FMT_STAMP "%lld\r\n"#endif

  • server.c

    #include<stdio.h>
#include<stdlib.h>
#include<sys/types.h>
#include<sys/socket.h>
#include<arpa/inet.h>
#include<time.h>
#include<unistd.h>#include"proto.h"#define IPSTRSIZE 40
#define BUFSIZE   1024static void server_job(int sd)
{int len;char buf[BUFSIZE];len = sprintf(buf,FMT_STAMP,(long long)time(NULL));if(send(sd,buf,len,0) < 0){perror("sen()");exit(1);}}int main()
{int sd,newsd;struct sockaddr_in laddr,raddr;socklen_t raddr_len;char ipstr[IPSTRSIZE];sd = socket(AF_INET,SOCK_STREAM,0/*IPPROTO_TCP*/);if(sd < 0){perror("socket()");exit(1);}laddr.sin_family = AF_INET;laddr.sin_port = htons(atoi(SERVERPORT));inet_pton(AF_INET,"0.0.0.0",&laddr.sin_addr);if(bind(sd,(void*)&laddr,sizeof(laddr)) < 0){perror("bind()");exit(1);}if(listen(sd,200)<0)//200全连接上限{perror("listen()");exit(1);}raddr_len = sizeof(raddr);while(1){newsd = accept(sd,(void*)&raddr,&raddr_len);if(newsd < 0){perror("accept()");exit(1);}inet_ntop(AF_INET,&raddr.sin_addr,ipstr,IPSTRSIZE);printf("Client:%s:%d\n",ipstr,ntohs(raddr.sin_port));server_job(newsd); //send()close(newsd);}close(sd);exit(0);
}

  • client.c

    #include<stdio.h>
#include<stdlib.h>
#include<sys/types.h>
#include<sys/socket.h>
#include<arpa/inet.h>#include"proto.h"int main(int argc, char **argv)
{int sd;struct sockaddr_in raddr;long long stamp;FILE *fp;if(argc < 2){fprintf(stderr,"Usage:...\n");exit(1);}sd = socket(AF_INET,SOCK_STREAM,0);if(sd < 0){perror("bind()");exit(1);}//bind();raddr.sin_family = AF_INET;raddr.sin_port =  htons(atoi(SERVERPORT));inet_pton(AF_INET,argv[1],&raddr.sin_addr); //server ipif(connect(sd,(void*)&raddr,sizeof(raddr)) < 0){perror("connet()");exit(1);}//一切皆文件:socket转为stream操作fp = fdopen(sd,"r+");if(fp == NULL){perror("fdopen()");exit(1);}if(fscanf(fp, FMT_STAMP, &stamp) < 1) //返回成功匹配的个数fprintf(stderr,"Bad format!\n");elsefprintf(stdout,"stamp = %lld\n",stamp);fclose(fp);//rcve()//close()exit(0);
}

运行结果：

./server

./server

或 发送请求

nc ip port 或 telnet ip port 发送请求

Untitled

注意点查看多线程部分。

多进程

示例代码：

  • server.c 其他不变

    #include<stdio.h>
#include<stdlib.h>
#include<sys/types.h>
#include<sys/socket.h>
#include<arpa/inet.h>
#include<time.h>
#include<unistd.h>
#include<sys/types.h>
#include<sys/wait.h>#include"proto.h"#define IPSTRSIZE 40
#define BUFSIZE   1024static void server_job(int sd)
{int len;char buf[BUFSIZE];len = sprintf(buf,FMT_STAMP,(long long)time(NULL));if(send(sd,buf,len,0) < 0){perror("sen()");exit(1);}}int main()
{int sd,newsd;struct sockaddr_in laddr,raddr;socklen_t raddr_len;char ipstr[IPSTRSIZE];pid_t pid;sd = socket(AF_INET,SOCK_STREAM,0/*IPPROTO_TCP*/);if(sd < 0){perror("socket()");exit(1);}int val=1;if(setsockopt(sd,SOL_SOCKET,SO_REUSEADDR,&val,sizeof(val)) < 0){perror("setsockopt()");exit(1);}laddr.sin_family = AF_INET;laddr.sin_port = htons(atoi(SERVERPORT));inet_pton(AF_INET,"0.0.0.0",&laddr.sin_addr);if(bind(sd,(void*)&laddr,sizeof(laddr)) < 0){perror("bind()");exit(1);}if(listen(sd,200)<0)//200全连接上限{perror("listen()");exit(1);}raddr_len = sizeof(raddr);while(1){// printf("****before accept****\n");newsd = accept(sd,(void*)&raddr,&raddr_len);// printf("****after accept****\n");if(newsd < 0){perror("accept()");exit(1);}pid = fork();if(pid < 0){perror("fork()");exit(1);}if(pid == 0){close(sd);inet_ntop(AF_INET,&raddr.sin_addr,ipstr,IPSTRSIZE);printf("Client:%s:%d\n",ipstr,ntohs(raddr.sin_port));server_job(newsd); //send()close(newsd);exit(0);}// printf("****end*****\n");close(newsd); //!!!}close(sd);exit(0);
}

运行结果：

Untitled

  1. 进程阻塞在 accept ，因为 accept 互斥访问和阻塞

如果父进程调用了 accept 产生了 newsd ，如果不关闭 newsd 会导致 accept 认为该上次的传输没有结束，会继续等待上一个连接结束，导致新的传输阻塞，这提醒我们 accept 得到的文件描述符要及时关闭

Untitled

  1. server 异常结束时，端口未释放，再次执行时无法立刻重新绑定端口， bind() 抛异常

    Untitled

    查看，端口未释放，无法立即绑定

    netstat -anu 查看，端口未释放，无法立即绑定

解决：设置 sockopt ： man 7 socket 查看socket层的表示，找到对应命令，执行 setsockopt()

setsockopt(sd,SOL_SOCKET,SO_REUSEADDR,&val,sizeof(val))

Untitled

pool_static：静态进程池

思路：预先创建四个进程，不断接收信息

示例代码：

  • server.c 其他不变

    #include<stdio.h>
#include<stdlib.h>
#include<sys/types.h>
#include<sys/socket.h>
#include<arpa/inet.h>
#include<time.h>
#include<unistd.h>
#include<sys/wait.h>#include"proto.h"#define IPSTRSIZE 40
#define BUFSIZE   1024
#define PROCNUM   4static void server_loop(int sd);
static void server_job(int sd)
{int len;char buf[BUFSIZE];len = sprintf(buf,FMT_STAMP,(long long)time(NULL));if(send(sd,buf,len,0) < 0){perror("send()");exit(1);}}int main()
{int sd,i;struct sockaddr_in laddr;pid_t pid;sd = socket(AF_INET,SOCK_STREAM,0/*IPPROTO_TCP*/);if(sd < 0){perror("socket()");exit(1);}int val=1;if(setsockopt(sd,SOL_SOCKET,SO_REUSEADDR,&val,sizeof(val)) < 0){perror("setsockopt()");exit(1);}laddr.sin_family = AF_INET;laddr.sin_port = htons(atoi(SERVERPORT));inet_pton(AF_INET,"0.0.0.0",&laddr.sin_addr);if(bind(sd,(void*)&laddr,sizeof(laddr)) < 0){perror("bind()");exit(1);}if(listen(sd,200)<0)//200全连接上限{perror("listen()");exit(1);}for(i = 0; i < PROCNUM; i++){pid = fork();if(pid < 0){perror("fork()");exit(1);}if(pid == 0){server_loop(sd);exit(0);}}for(i = 0; i < PROCNUM; i++)wait(NULL);close(sd); //!!!exit(0);
}static void server_loop(int sd)
{struct sockaddr_in raddr;socklen_t raddr_len;int newsd;char ipstr[IPSTRSIZE];raddr_len = sizeof(raddr);while(1){//accept本身实现了互斥和阻塞，所以不用互斥量或信号量数组或条件变量newsd = accept(sd,(void*)&raddr,&raddr_len);if(newsd < 0){perror("accept()");exit(1);}inet_ntop(AF_INET,&raddr.sin_addr,ipstr,IPSTRSIZE);printf("[%d]Client:%s:%d\n",getpid(),ipstr,ntohs(raddr.sin_port));server_job(newsd); //send()close(newsd);}
}

运行结果：

Untitled

缺点：无法应对突发请求，没有弹性

pool_dynamic：动态进程池

  • server.c其他不变

    #include<stdio.h>
#include<stdlib.h>
#include<sys/types.h>
#include<sys/socket.h>
#include<arpa/inet.h>
#include<signal.h>
#include<errno.h>
#include<unistd.h>
#include<sys/mman.h>
#include<time.h>#include"proto.h"#define MINSPARESERVER 5
#define MAXSPARESERVER 10
#define MAXCLIENTS     20#define SIG_NOTIFY     SIGUSR2
#define IPSTRSIZE      40
#define LINEBUFSIZE    80enum
{STATE_IDLE=0,STATE_BUSY
};struct server_st
{pid_t pid;int state;
//  int reuse;};static struct server_st *serverpool;
static int idle_count = 0, busy_count = 0;
static int sd;static void usr2_handler(int s)
{return;
}static void server_job(int pos)
{pid_t ppid;struct sockaddr_in raddr;socklen_t raddr_len,len;int client_sd;time_t stamp;char ipstr[IPSTRSIZE];char linebuf[LINEBUFSIZE];ppid = getppid();while(1){serverpool[pos].state = STATE_IDLE;kill(ppid,SIG_NOTIFY);//发信号通知父进程client_sd = accept(sd,(void*)&raddr,&raddr_len);if(client_sd < 0){if(errno != EINTR && errno != EAGAIN){perror("accpet()");exit(1);}}serverpool[pos].state = STATE_BUSY;kill(ppid,SIG_NOTIFY);//inet_ntop(AF_INET,&raddr.sin_addr,ipstr,IPSTRSIZE);//printf("[%d]client:%s:%d\n",getpid(),ipstr,ntohs(raddr.sin_port));stamp = time(NULL);len = snprintf(linebuf, LINEBUFSIZE, FMT_STAMP,stamp);send(client_sd, linebuf, len, 0);/*if error*/sleep(5);close(client_sd);}
}static int add_1_server(void)
{int slot;pid_t pid;if(idle_count + busy_count >= MAXCLIENTS)return -1;for(slot = 0; slot < MAXCLIENTS; slot++){if(serverpool[slot].pid == -1)break;}serverpool[slot].state = STATE_IDLE;pid = fork();if(pid < 0){perror("fork()");exit(1);}if(pid == 0)    //child{server_job(slot);exit(0);}   else            //parent{serverpool[slot].pid = pid;idle_count++;}return 0;
}static int del_1_server(void)
{int i;if(idle_count == 0)return -1;for(i=0; i < MAXCLIENTS; i++){if(serverpool[i].pid != -1 && serverpool[i].state == STATE_IDLE){kill(serverpool[i].pid, SIGTERM);serverpool[i].pid = -1;idle_count--;break;}}return 0;
}static int scan_pool(void)
{int i;int busy = 0, idle = 0;for(i = 0; i < MAXCLIENTS; i++){if(serverpool[i].pid == -1)continue;if(kill(serverpool[i].pid,0)){serverpool[i].pid = -1;continue;}if(serverpool[i].state == STATE_IDLE)idle++;else if(serverpool[i].state == STATE_BUSY)busy++;else{fprintf(stderr,"Unknow state.\n");// _exit(1);abort();}}idle_count = idle;busy_count = busy;return 0;
}int main()
{struct sigaction sa,o_sa;struct sockaddr_in laddr;sigset_t set,oset;//功能：子进程会自行消亡，不用父进程收尸sa.sa_handler = SIG_IGN;sigemptyset(&sa.sa_mask);sa.sa_flags = SA_NOCLDWAIT;sigaction(SIGCHLD,&sa,&o_sa);//设置SIGNOTIFY信号处理函数sa.sa_handler = usr2_handler;sigemptyset(&sa.sa_mask);sa.sa_flags = 0;sigaction(SIG_NOTIFY,&sa,&o_sa);//父进程屏蔽SIGNOTIFYsigemptyset(&set);sigaddset(&set,SIG_NOTIFY);sigprocmask(SIG_BLOCK,&set,&oset);serverpool = mmap(NULL,sizeof(struct server_st)*MAXCLIENTS,PROT_READ|PROT_WRITE,MAP_SHARED|MAP_ANONYMOUS,-1,0);//mallocif(serverpool == MAP_FAILED){perror("mmap()");exit(1);}int i;for(i = 0; i < MAXCLIENTS; i++){serverpool[i].pid = -1;}sd = socket(AF_INET,SOCK_STREAM,0);if(sd < 0){perror("socket()");exit(1);}int val = 1;if(setsockopt(sd,SOL_SOCKET,SO_REUSEADDR,&val,sizeof(val)) < 0){perror("setsockopt()");exit(1);}laddr.sin_family = AF_INET;laddr.sin_port = htons(atoi(SERVERPORT));inet_pton(AF_INET,"0.0.0.0",&laddr.sin_addr);if(bind(sd,(void*)&laddr,sizeof(laddr)) < 0){perror("bind()");exit(1);}if(listen(sd,100) < 0){perror("listen()");exit(1);}for(i = 0; i < MINSPARESERVER; i++){add_1_server();}//信号驱动程序while(1){sigsuspend(&oset);scan_pool();//control the poolif(idle_count > MAXSPARESERVER){for(i=0;i<(idle_count-MAXSPARESERVER);i++)del_1_server();}else if(idle_count<MINSPARESERVER){for(i=0;i<(MINSPARESERVER-idle_count);i++)add_1_server();}//printf the pool statefor(i=0; i < MAXCLIENTS; i++){if(serverpool[i].pid == -1)putchar('*');else if(serverpool[i].state == STATE_IDLE)putchar('.');elseputchar('x');}putchar('\n');}sigprocmask(SIG_SETMASK,&oset,NULL); //恢复// close();exit(0);
}

运行结果：

  1. * ：未创建
  2. . ：空闲
  3. x ：busy

client：

Untitled

client*1

client*2

client*3

clietn*4

注意：

因为 server_st 数组是 mmap 出来的，所以父子进程都可见。

scan_pool 的时候更新 idle_count 计数

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