Socket多进程

OVERVIEW

• Socket多进程
• • • • 1.Server
      • 2.Client
      • 3.bug&rethink
      • 4.source code

调用socket、connect、bind、listen、accept、send、recv

1.Server

//1.server.c
#include "head.h"
#include "common.h"#define handle_error(msg) \do { perror(msg); exit(EXIT_FAILURE); } while (0)int main(int argc, char *argv[]) {//./a.out -p port//1.命令行解析if (argc != 3) {fprintf(stderr, "Usage : %s -p port", argv[0]);exit(1);}int opt;int port;int sockfd;while ((opt = getopt(argc, argv, "p:")) != -1) {switch (opt) {case 'p':port = atoi(optarg);break;default:fprintf(stderr, "Usage : %s -p port\n", argv[0]);exit(1);}}//2.创建socketif ((sockfd = socketCreate(port)) < 0) handle_error("socketCreate");//3.accept循环的接受客户端对server的连接while (1) {int newfd;if ((newfd = accept(sockfd, NULL, NULL)) < 0) handle_error("accept");//不关注客户端的ip地址与端口号NULLprintf(" : accept a client!\n");//4.recv接受到消息while (1) {char buff[1024] = {0};ssize_t rsize = recv(newfd, buff, sizeof(buff), 0);if (rsize > 0) printf(" : %s\n", buff);}}return 0;
}

//common.h
#ifndef _COMMON_H
#define _COMMON_Hint socketCreate(int port);#endif

//common.c
#include "head.h"int socketCreate(int port) {//1.创建套接字int sockfd;struct sockaddr_in addr;if ((sockfd = socket(AF_INET, SOCK_STREAM, 0)) < 0) return -1;addr.sin_family = AF_INET;addr.sin_port = htons(port);//主机字节序转换为网络字节序addr.sin_addr.s_addr = inet_addr("0.0.0.0");//将网络字节序转化为主机字节序 0.0.0.0表示不关注消息传来的地址//2.bind绑定套接字与结构体信息 listenif (bind(sockfd, (struct sockaddr *)&addr, sizeof(struct sockaddr)) < 0) return -1;if (listen(sockfd, 20) < 0) return -1;return sockfd;
} 

将2000端口作为服务端绑定的端口，启动服务端程序

新建一个窗口利用netstat -alnt命令查看已经在使用的端口及其当前状态：LISTEN

利用telnet ip port命令对服务端进行测试（需要开放阿里云服务器安全组，并设置linux系统的防火墙才能进行测试）：

服务端接收到消息并receive打印输出消息：

可以看到服务端成功接收到消息，并打印了消息内容。

2.Client

#include "head.h"#define handle_error(msg) \do { perror(msg); exit(EXIT_FAILURE); } while (0)int main(int argc, char *argv[]) {//./a.out ip portif (argc != 3) {fprintf(stderr, "Usage : %s ip port\n", argv[0]);exit(1);}//1.客户端打开一个socketint sockfd;if ((sockfd = socket(AF_INET, SOCK_STREAM, 0)) < 0) handle_error("socket");//2.定义结构体用于绑定端口号、ip地址（存放服务端的具体信息）struct sockaddr_in server;server.sin_family = AF_INET;server.sin_port = htons(atoi(argv[2]));//端口号server.sin_addr.s_addr = inet_addr(argv[1]);//ip地址//3.建立连接connectionif (connect(sockfd, (struct sockaddr *)&server, sizeof(server)) < 0) handle_error("connect");//4.send发送数据while (1) {//循环发送消息char buff[1024] = {0};scanf("%[^\n]s", buff);//输入可含空格的字符串getchar();//吞掉一个换行//只要向文件描述符中写入 tcp服务就会帮助发送消息//With a zero flags argument, send is equivalent to write(2).if (strlen(buff)) send(sockfd, buff, sizeof(buff), 0);}return 0;
}

同时启动客户端与服务端，从客户端发送消息，可以看到服务端能够正常接收消息并打印：

3.bug&rethink

程序还有几个功能上没有处理的bug：

1. 客户端ctrl+C结束之后，服务端无法接收到客户端退出连接的状态。
2. 如果创建多个客户端尝试连接服务端，服务端将无法接收到客户端的连接请求。
3. 服务端能够知道是谁向我发送的数据（打印出客户端的ip地址和端口号）

问题1解决：在client.c中利用signal信号，并添加一个closeSock函数对客户端ctrl+c后向服务端做出相应：

#include "head.h"#define handle_error(msg) \do { perror(msg); exit(EXIT_FAILURE); } while (0)int sockfd;//ctrl+c信号处理
void closeSock(int signum) {send(sockfd, " : I am leaving...", 27, 0);close(sockfd);exit(1);
}int main(int argc, char *argv[]) {//./a.out ip portif (argc != 3) {fprintf(stderr, "Usage : %s ip port\n", argv[0]);exit(1);}//1.客户端打开一个socketif ((sockfd = socket(AF_INET, SOCK_STREAM, 0)) < 0) handle_error("socket");//2.定义结构体用于绑定端口号、ip地址（存放服务端的具体信息）struct sockaddr_in server;server.sin_family = AF_INET;server.sin_port = htons(atoi(argv[2]));//端口号server.sin_addr.s_addr = inet_addr(argv[1]);//ip地址signal(SIGINT, closeSock);//3.建立连接connectionif (connect(sockfd, (struct sockaddr *)&server, sizeof(server)) < 0) handle_error("connect");printf("connect sccuess!\n");//4.send发送数据while (1) {//循环发送消息char buff[1024] = {0};scanf("%[^\n]s", buff);//输入可含空格的字符串getchar();//吞掉一个换行//只要向文件描述符中写入 tcp服务就会帮助发送消息//With a zero flags argument, send is equivalent to write(2).if (strlen(buff)) send(sockfd, buff, sizeof(buff), 0);}return 0;
}

问题2解决：在server.c中fork多个进程，父进程用于accept、子进程用于receive并将接受到的信息进行打印。

#include "head.h"
#include "common.h"#define handle_error(msg) \do { perror(msg); exit(EXIT_FAILURE); } while (0)int main(int argc, char *argv[]) {//./a.out -p port//1.命令行解析if (argc != 3) {fprintf(stderr, "Usage : %s -p port", argv[0]);exit(1);}int opt;int port;int sockfd;while ((opt = getopt(argc, argv, "p:")) != -1) {switch (opt) {case 'p':port = atoi(optarg);break;default:fprintf(stderr, "Usage : %s -p port\n", argv[0]);exit(1);}}//2.创建socketif ((sockfd = socketCreate(port)) < 0) handle_error("socketCreate");//3.accept循环的接受客户端对server的连接while (1) {int pid;int newfd;//新建的文件描述符if ((newfd = accept(sockfd, NULL, NULL)) < 0) handle_error("accept");//不关注客户端的ip地址与端口号NULLprintf(" : accept a client!\n");//4.子进程recv接受到消息if ((pid = fork()) < 0) handle_error("fork");if (pid == 0) {//子进程进行操作while (1) {char buff[1024] = {0};ssize_t rsize = recv(newfd, buff, sizeof(buff), 0);if (rsize > 0) {printf(" : %s\n", buff);} else {close(sockfd);break;}}printf(" : a client left!\n");exit(0);}}return 0;
}

问题3解决：在server.c中对accept函数位置进行修改，获取到client端的具体信息显示并打印在聊天的过程中：

#include "head.h"
#include "common.h"#define handle_error(msg) \do { perror(msg); exit(EXIT_FAILURE); } while (0)int main(int argc, char *argv[]) {//./a.out -p port//1.命令行解析if (argc != 3) {fprintf(stderr, "Usage : %s -p port", argv[0]);exit(1);}int opt;int port;int sockfd;while ((opt = getopt(argc, argv, "p:")) != -1) {switch (opt) {case 'p':port = atoi(optarg);break;default:fprintf(stderr, "Usage : %s -p port\n", argv[0]);exit(1);}}//2.创建socketif ((sockfd = socketCreate(port)) < 0) handle_error("socketCreate");//3.accept循环的接受客户端对server的连接while (1) {int pid;int newfd;//新建的文件描述符struct sockaddr_in client;//用于存放临时建立连接的客户端的信息socklen_t len = sizeof(client);if ((newfd = accept(sockfd, (struct sockaddr *)&client, &len)) < 0) handle_error("accept");//不关注客户端的ip地址与端口号NULLprintf(" %s:%d: accept a client!\n", inet_ntoa(client.sin_addr), ntohs(client.sin_port));//4.子进程recv接受到消息if ((pid = fork()) < 0) handle_error("fork");if (pid == 0) {//子进程进行操作while (1) {char buff[1024] = {0};ssize_t rsize = recv(newfd, buff, sizeof(buff), 0);//三次握手四次挥手if (rsize > 0) {printf(" %s:%d: %s\n", inet_ntoa(client.sin_addr), ntohs(client.sin_port), buff);} else {close(sockfd);break;}}printf(" : %s:%d left!\n", inet_ntoa(client.sin_addr), ntohs(client.sin_port));exit(0);}}return 0;
}

遗留bug：在多个客户端与服务端建立连接后，服务端先于客户端关闭，而客户端未收到通知则会产生CLOSE_WAIT与FIN_WAIT2端口状态（导致端口重用出现报错问题，端口无效占用，系统端口很快将被用尽）。

4.source code

//common.h
#ifndef _COMMON_H
#define _COMMON_Hint socketCreate(int port);
int socketConnect(const char *ip, int port);#endif

//common.c
#include "head.h"int socketCreate(int port) {//1.创建套接字int sockfd;struct sockaddr_in addr;if ((sockfd = socket(AF_INET, SOCK_STREAM, 0)) < 0) return -1;addr.sin_family = AF_INET;addr.sin_port = htons(port);//主机字节序转换为网络字节序addr.sin_addr.s_addr = inet_addr("0.0.0.0");//将网络字节序转化为主机字节序 0.0.0.0表示不关注消息传来的地址//2.bind绑定套接字与结构体信息 listenif (bind(sockfd, (struct sockaddr *)&addr, sizeof(struct sockaddr)) < 0) return -1;if (listen(sockfd, 20) < 0) return -1;return sockfd;
}int socketConnect(const char *ip, int port) {int sockfd;//1.客户端打开一个socketif ((sockfd = socket(AF_INET, SOCK_STREAM, 0)) < 0) return -1;//2.定义结构体用于绑定端口号、ip地址（存放服务端的具体信息）struct sockaddr_in server;server.sin_family = AF_INET;server.sin_port = htons(port);//端口号server.sin_addr.s_addr = inet_addr(ip);//ip地址//3.建立连接connectionif (connect(sockfd, (struct sockaddr *)&server, sizeof(server)) < 0) return -1;return sockfd;
}

//server.c
#include "head.h"
#include "common.h"#define handle_error(msg) \do { perror(msg); exit(EXIT_FAILURE); } while (0)int main(int argc, char *argv[]) {//./a.out -p port//1.命令行解析if (argc != 3) {fprintf(stderr, "Usage : %s -p port", argv[0]);exit(1);}int opt;int port;int sockfd;while ((opt = getopt(argc, argv, "p:")) != -1) {switch (opt) {case 'p':port = atoi(optarg);break;default:fprintf(stderr, "Usage : %s -p port\n", argv[0]);exit(1);}}//2.创建socketif ((sockfd = socketCreate(port)) < 0) handle_error("socketCreate");//3.accept循环的接受客户端对server的连接while (1) {int pid;int newfd;//新建的文件描述符struct sockaddr_in client;//用于存放临时建立连接的客户端的信息socklen_t len = sizeof(client);if ((newfd = accept(sockfd, (struct sockaddr *)&client, &len)) < 0) handle_error("accept");//不关注客户端的ip地址与端口号NULLprintf(" %s:%d: accept a client!\n", inet_ntoa(client.sin_addr), ntohs(client.sin_port));//4.子进程recv接受到消息if ((pid = fork()) < 0) handle_error("fork");if (pid == 0) {//子进程进行操作while (1) {char buff[1024] = {0};ssize_t rsize = recv(newfd, buff, sizeof(buff), 0);//三次握手四次挥手if (rsize > 0) {printf(" %s:%d: %s\n", inet_ntoa(client.sin_addr), ntohs(client.sin_port), buff);} else {close(sockfd);break;}}printf(" : %s:%d has left!\n", inet_ntoa(client.sin_addr), ntohs(client.sin_port));exit(0);}}return 0;
}

//client.c
#include "head.h"
#include "common.h"#define handle_error(msg) \do { perror(msg); exit(EXIT_FAILURE); } while (0)int sockfd;//ctrl+c信号处理
void closeSock(int signum) {send(sockfd, "I am leaving...", 27, 0);close(sockfd);exit(0);
}int main(int argc, char *argv[]) {//./a.out ip portif (argc != 3) {fprintf(stderr, "Usage : %s ip port\n", argv[0]);exit(1);}signal(SIGINT, closeSock);//1.建立连接connectif ((sockfd = socketConnect(argv[1], atoi(argv[2]))) < 0) handle_error("socketConnect");printf("connect sccuess!\n");//2.send发送数据while (1) {//循环发送消息char buff[1024] = {0};scanf("%[^\n]s", buff);//输入可含空格的字符串getchar();//吞掉一个换行//只要向文件描述符中写入 tcp服务就会帮助发送消息//With a zero flags argument, send is equivalent to write(2).if (strlen(buff)) send(sockfd, buff, sizeof(buff), 0);}return 0;
}