1、高性能网络服务程序
Linux的一个应用优势是可用于设计各种高性能网络服务程序，高性能的一个特点就是实现并发访问处理，及同时为多个在线用户提供服务；多进程网络服务、多线程网络服务、线程池网络服务；
2、多进程网络服务
：利用Linux系统中的父子进程关系为多用户提供并发服务，是一种比较流行的并发服务技术，其基本理念是：来一个用户，启动一个服务进程。若有新连接到来，则启动子进程与其交互，服务结束后，其子进程自动退出。
模型如下：
3、代码实现：
用一个整数的运算模拟多进程的网络服务。
(1)、utili.h
#include#include#include#include#include#include#include#include#define SERVER_PORT 9090#define SERVER_IP "127.0.0.1"#define LISTEN_QUEUE 5#define BUFFER_SIZE 255typedef enum{ADD,SUB,MUL,DIV,MOD, QUIT}OPER_TYPE;typedef struct OperStruct{
int op1;
int op2;
OPER_TYPE oper;}OperStruct;
(2)、ser.c
#include"../utili.h"void Process_Handler(int sockConn);void Process_Handler(int sockConn){
OperStruct op;
int result;
while(1){
int res = recv(sockConn, &op, sizeof(op), 0);
if(res == -1){
printf("recv data fail.\n");
continue;
}
if(op.oper == ADD){
result = op.op1 + op.op2;
}else if(op.oper == SUB)
{
result = op.op1 - op.op2;
}else if(op.oper == MUL){
result = op.op1 * op.op2;
}else if(op.oper == DIV){
result = op.op1 / op.op2;
}else if(op.oper == QUIT){
break;
}
res = send(sockConn, &result, sizeof(result), 0);
if(res == -1){
printf("send data fail.\n");
continue;
}
}
close(sockConn);}int main(void){
int sockSer = socket(AF_INET, SOCK_STREAM, 0);
if(sockSer == -1){
perror("socket");
return -1;
}
struct sockaddr_in addrSer, addrCli;
addrSer.sin_family = AF_INET;
addrSer.sin_port = htons(SERVER_PORT);
addrSer.sin_addr.s_addr = inet_addr(SERVER_IP);
socklen_t len = sizeof(struct sockaddr);
int res = bind(sockSer, (struct sockaddr*)&addrSer, len);
if(res == -1){
perror("bind");
close(sockSer);
return -1;
}
listen(sockSer, LISTEN_QUEUE);
int sockConn;
while(1){
printf("Server Wait Client Connect.......\n");
sockConn = accept(sockSer, (struct sockaddr*)&addrCli, &len);
if(sockConn == -1){
printf("Server Accept Client Connect Fail.\n");
continue;
}else{
printf("Server Accept Client Connect Success.\n");
printf("Client IP:>%s\n", inet_ntoa(addrCli.sin_addr));
printf("Client Port:>%d\n",ntohs(addrCli.sin_port));
}
pid_t pid;
pid = fork();
if(pid == 0){
close(sockSer);
Process_Handler(sockConn);
exit(0);
}else if(pid > 0){
close(sockConn);
continue;
}else{
printf("Create Process Fail.\n");
continue;
}
}
close(sockSer);
return 0;}
(3)、cli.c
#include"utili.h"void InputData(OperStruct *pt);void InputData(OperStruct *pt){
printf("please input op1 and op2 : ");
scanf("%d %d", &(pt->op1), &(pt->op2));}//Cliint main(void){
int sockCli = socket(AF_INET, SOCK_STREAM, 0);
if(sockCli == -1){
perror("socket");
return -1;
}
struct sockaddr_in addrSer;
addrSer.sin_family = AF_INET;
addrSer.sin_port = htons(SERVER_PORT);
addrSer.sin_addr.s_addr = inet_addr(SERVER_IP);
socklen_t len = sizeof(struct sockaddr);
int res = connect(sockCli, (struct sockaddr*)&addrSer, len);
if(res == -1){
perror("connect");
close(sockCli);
return -1;
}else{
printf("Client Connect Server Success.\n");
}
char cmd[2];
OperStruct op;
int result;
while(1){
printf("Please input operator : ");
scanf("%s",cmd);
if(strcmp(cmd, "+") == 0){
op.oper = ADD;
InputData(&op);
}else if(strcmp(cmd,"-") == 0){
op.oper = SUB;
InputData(&op);
}else if(strcmp(cmd,"*") == 0){
op.oper = MUL;
InputData(&op);
}else if(strcmp(cmd,"/") == 0){
op.oper = DIV;
InputData(&op);
}else if(strcmp(cmd, "quit") == 0){
op.oper = QUIT;
}else{
printf("Cmd invalid.\n");
}
res = send(sockCli, &op, sizeof(op), 0);
if(res == -1){
printf("send data fail.\n");
continue;
}
if(op.oper == QUIT)
break;
res = recv(sockCli, &result, sizeof(result), 0);
if(res == -1){
printf("recv data fail.\n");
continue;
}
printf("result = %d\n", result);
}
close(sockCli);
return 0;}
运行结果：
服务器端
客户1
客户1
客户2
4、结果分析
(1)、utili.h在ser.c的上一层目录，utili.h和cli.c是在同一层目录；
(2)、进程服务器：socker是引用计数器模型，close()是减少一个，并没有真正的关闭，每次创建一个进程都会给socker引用计数器加1；
(3)、缺点：a、启动和关闭子进程带来很大的开销；b、系统最多只能产生512个进程，也就是说最多只有512个客户，形成不了处理大型访问的情形；
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