原创【博客大赛】socket通信的简单示例

 2016-6-2 20:03  1259 17 17 分类: MCU/ 嵌入式文集: Qt和Cpp

假设有两个进程（RoseGarden和WeatherForecast）之间需要通信，其中前者作为服务器，后者作为客户端。
这里的socket使用最常见的domain(AF_INET，即IPV4），使用的通讯类型为SOCK_STREAM。

服务器端代码如下：
#include <iostream>
#include <unistd.h>
#include <memory.h>
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/msg.h>
#include <sys/shm.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <netinet/in.h>
#include <syslog.h>
#include <fcntl.h>
#include <sys/resource.h>
#include <signal.h>
#include <syslog.h>
#include <arpa/inet.h>
#include <vector>
using namespace std;

int main() {
   cout << "*****************************" << endl;
   cout << "******* RoseGarden ********" << endl;
   cout << "*****************************" << endl;

   string hostname = "localhost.localdomain";
   string servname = "hello";

   struct addrinfo hint;
   memset(&hint, 0, sizeof(hint));
   hint.ai_flags = AI_CANONNAME;
   hint.ai_socktype = SOCK_STREAM;
   hint.ai_canonname = NULL;
   hint.ai_addr = NULL;
   hint.ai_next = NULL;

   int err;
   struct addrinfo *ailist, *aip;
   if ((err = getaddrinfo(hostname.data(), servname.data(), &hint, &ailist)) != 0) {
       cerr << "<RoseGarden> Error: " << gai_strerror(err) << endl;
       exit(1);
   }
   vector<int> sockfd;
   int fd;
   for (aip = ailist; aip != NULL; aip = aip->ai_next) {
       if ((fd = socket(aip->ai_family, aip->ai_socktype, aip->ai_protocol)) < 0)
           continue;
       if (bind(fd, aip->ai_addr, aip->ai_addrlen) < 0) {
           close(fd);
           continue;
       }
       if (listen(fd, 1) < 0) {
           close(fd);
           continue;
       }
       sockfd.push_back(fd);
       cout << "<RoseGarden> valid SOCKFD = " << fd << endl;
   }

   int clfd;
   clfd = accept(sockfd[0], NULL, NULL);
   cout << "<RoseGarden> valid CLIENT SOCKFD = " << clfd << endl;

   int count;
   string sbuf;
   while (1) {
       sbuf = "<RoseGarden> " + to_string(count++) + " message.";
       send(clfd, sbuf.data(), sbuf.size(), 0);
       sleep(1);
   }
   return 0;
}

客户端代码如下：
#include <iostream>
#include <unistd.h>
#include <memory.h>
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/msg.h>
#include <sys/shm.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <netinet/in.h>
#include <syslog.h>
#include <fcntl.h>
#include <sys/resource.h>
#include <signal.h>
#include <syslog.h>
#include <arpa/inet.h>
#include <vector>
using namespace std;

int main(int argc, char *argv[])
{
   cout << "*****************************" << endl;
   cout << "***** WeatherForecast *****" << endl;
   cout << "*****************************" << endl;

   if (argv[1] == NULL) {
       cerr << "Error: Please input address and service-name." << endl;
       exit(1);
   }
   if (argv[2] == NULL) {
       cerr << "Error: Please input service-name." << endl;
       exit(1);
   }

   struct addrinfo hint;
   memset(&hint, 0, sizeof(hint));
   hint.ai_flags = AI_CANONNAME;
   hint.ai_socktype = SOCK_STREAM;
   hint.ai_canonname = NULL;
   hint.ai_addr = NULL;
   hint.ai_next = NULL;

   int err;
   struct addrinfo *ailist, *aip;
   if ((err = getaddrinfo(argv[1], argv[2], &hint, &ailist)) != 0) {
       cerr << "<WeatherForcast> Error: " << gai_strerror(err) << endl;
       exit(1);
   }
   vector<int> sockfd;
   int fd;
   for (aip = ailist; aip != NULL; aip = aip->ai_next) {
       if ((fd = socket(aip->ai_family, aip->ai_socktype, aip->ai_protocol)) < 0)
           continue;
       if (connect(fd, aip->ai_addr, aip->ai_addrlen) != 0) {
           close(fd);
           continue;
       }
       sockfd.push_back(fd);
       cout << "<WeatherForcast> valid SOCKFD = " << fd << endl;
   }

   char rbuf[128];
   int n;
   while (1) {
       memset(rbuf, 0, sizeof(rbuf));
       n = recv(sockfd[0], rbuf, sizeof(rbuf), 0);
       if (n > 0)
           cout << "<WeatherForcase> R: " << rbuf << endl;
   }
   return 0;
}

客户端执行结果：
$ ./RoseGarden
*****************************
******* RoseGarden ********
*****************************
<RoseGarden> valid SOCKFD = 3
<RoseGarden> valid CLIENT SOCKFD = 4

服务器端执行结果：
$ ./WeatherForecast 127.0.0.1 hello
*****************************
***** WeatherForecast *****
*****************************
<WeatherForcast> valid SOCKFD = 3
<WeatherForcase> R: <RoseGarden> 0 message.
<WeatherForcase> R: <RoseGarden> 1 message.
<WeatherForcase> R: <RoseGarden> 2 message.
<WeatherForcase> R: <RoseGarden> 3 message.
<WeatherForcase> R: <RoseGarden> 4 message.
<WeatherForcase> R: <RoseGarden> 5 message.

虽然socket的原理很复杂，它使用起来却很简单。
《Unix环境高级编程》这本书的第16章讲的就是socket的用法。
刚开始看的时候，可能会被很多数量的结构体和函数绕晕了，但是没关系，看第二遍的时候就会清晰很多。
ps：多实验代码，将结构体的值打印出来观察～