近日研究socket 通信，学习了如下的一篇文章：
(向作者致敬)
感觉很好，但还有一点不过瘾，就想着能否加点料:增加多个客户端，让他们一起和服务器端通信。
为了区别各个客户端，把客户端里加入了识别自身hostname的一段。
修改后的代码如下：
server ：
#include#include #include #include #include #include #include #include #include #define HELLO_WORLD_SERVER_PORT 6666#define LENGTH_OF_LISTEN_QUEUE 20#define BUFFER_SIZE 1024void reaper(int sig){int status;while( wait3(&status,WNOHANG,(struct rusage*)0) >=0 ) ;}int main(int argc, char **argv){ struct sockaddr_in server_addr; bzero(&server_addr,sizeof(server_addr)); server_addr.sin_family = AF_INET; server_addr.sin_addr.s_addr = htons(INADDR_ANY); server_addr.sin_port = htons(HELLO_WORLD_SERVER_PORT); int server_socket = socket(AF_INET,SOCK_STREAM,0); if( server_socket < 0){ printf("Create Socket Failed!"); exit(1); } if( bind(server_socket,(struct sockaddr*)&server_addr,sizeof(server_addr))){ printf("Server Bind Port : %d Failed!", HELLO_WORLD_SERVER_PORT); exit(1); } fprintf(stderr,"Before Main Process listen.\n"); if ( listen(server_socket, LENGTH_OF_LISTEN_QUEUE) ){ printf("Server Listen Failed!"); exit(1); } fprintf(stderr, "After Main Process listen.\n"); (void)signal(SIGCHLD,reaper); while (1){ struct sockaddr_in client_addr; socklen_t length = sizeof(client_addr); fprintf(stderr,"Before accept. In %d.\n",getpid()); int new_server_socket = accept(server_socket,(struct sockaddr*)&client_addr,&length); if ( new_server_socket < 0){ printf("Server Accept Failed!\n"); break; } fprintf(stderr,"After accept. In %d.\n",getpid()); int child_process_pid = fork(); if(child_process_pid == 0 ){ fprintf(stderr,"Child. %d born.\n",getpid()); close(server_socket); char buffer[BUFFER_SIZE]; bzero(buffer, BUFFER_SIZE); strcpy(buffer,"Hello,World! FromServer! "); int pd; pd=getpid(); char cpd[10]; sprintf(cpd,"%d",pd); strcat(buffer,cpd); strcat(buffer,"\n"); send(new_server_socket,buffer,BUFFER_SIZE,0); bzero(buffer,BUFFER_SIZE); length = recv(new_server_socket,buffer,BUFFER_SIZE,0); if (length < 0){ printf("Server Recieve Data Failed!\n"); exit(1); } fprintf(stderr,"got: %s in %d\n",buffer,getpid()); close(new_server_socket); exit(0); } else if(child_process_pid > 0) close(new_server_socket); } close(server_socket); return 0;}
client:
#include#include #include #include #include #include #include #define HELLO_WORLD_SERVER_PORT 6666#define BUFFER_SIZE 1024void talk_to_server(char ** argv){ struct sockaddr_in client_addr; bzero(&client_addr,sizeof(client_addr)); client_addr.sin_family = AF_INET; client_addr.sin_addr.s_addr = htons(INADDR_ANY); client_addr.sin_port = htons(0); int client_socket = socket(AF_INET,SOCK_STREAM,0); if( client_socket < 0){ printf("Create Socket Failed!\n"); exit(1); } if( bind(client_socket,(struct sockaddr*)&client_addr,sizeof(client_addr))){ printf("Client Bind Port Failed!\n"); exit(1); } struct sockaddr_in server_addr; bzero(&server_addr,sizeof(server_addr)); server_addr.sin_family = AF_INET; if(inet_aton(argv[1],&server_addr.sin_addr) == 0) { printf("Server IP Address Error!\n"); exit(1); } server_addr.sin_port = htons(HELLO_WORLD_SERVER_PORT); socklen_t server_addr_length = sizeof(server_addr); if( connect( client_socket, (struct sockaddr*)&server_addr, server_addr_length) < 0 ) { printf("Can Not Connect To %s!\n",argv[1]); exit(1); } char buffer[BUFFER_SIZE]; bzero(buffer,BUFFER_SIZE); int length = recv( client_socket, buffer,BUFFER_SIZE,0); if(length < 0){ printf("Recieve Data From Server %s Failed!\n", argv[1]); exit(1); } printf("From Server %s :\t%s",argv[1],buffer); bzero(buffer,BUFFER_SIZE); char name[64]; gethostname(name,sizeof(name)); strcpy(buffer,name); send(client_socket,buffer,BUFFER_SIZE,0); close(client_socket);}int main(int argc, char **argv){ if (argc != 2){ printf("Usage: ./%s ServerIPAddress\n",argv[0]); exit(1); } int i=0; for(i=0; i<10000; i++){ talk_to_server(argv); sleep(10); } return 0;}
然后，用三个机器，一个跑server,两个跑client。先运行server,再分别跑两个client，结果如下：
为了方便观察，略作整理：
Server端运行结果:
./con-server.o Before Main Process listen. After Main Process listen. Before accept. In 676. After accept. In 676 Child 678 born. Before accept. In 676. got : post2.gao in 678 After accept. In 676. Child 679 born. Before accept. In 676. got: post3.gao in 679. After accept. In 676. Child 680 born. Before accept. In 676. got: post2.gao in 680. After accept. In 676. Child. 681 born.Before accept. In 676. got: post3.gao in 681 ......
两个client端运行结果：
./con-client.o 192.168.66.136 From Server 192.168.66.136: Hello,World! From Server! 678 From Server 192.168.66.136: Hello,World! From Server! 680 ......
./con-client.o 192.168.66.136 From Server 192.168.66.136: Hello,World! From Server! 679 From Server 192.168.66.136: Hello,World! From Server! 681 ......
这样就成为多个客户端请求Server端。
此外也可以发现，listen动作不阻塞，accept动作阻塞。
服务器端主进程每当捕获到一个客户端请求，就fork一个子进程，
由子进程用 new_server_socket来send 和 recv工作。fork子进程后，工作完毕再消除的方法未必理想，今后有机会看看能否事先开一个进程池，来提升效率。