基于TCP协议：实现简单的多线程多进程服务器

为什么要多线程多进程服务器？

相比于UDP来说，由于UDP是不需要连接的，可直接通信。所以基于UDP协议的服务器，并不需要考虑到多客户端同时访问服务器时接受数据的问题。而TCP协议是需要连接的，在一个客户端连接上服务器后，这个时候服务器就开始于客户端进行消息的发送与接收。那么其它的客户端在这个时候是无法与服务器连接的。这个时候就需要考虑多线程或者多进程的服务器来应对这个问题了。

基于TCP协议：多进程服务器

//server.c
#include <stdio.h>
#include <unistd.h>
#include <sys/wait.h>
#include <stdlib.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <strings.h>

int StartUp(char* ip, char* port)
{
  if(ip == NULL || port == NULL) {
    return -1;
  }
  int sock = socket(AF_INET, SOCK_STREAM, 0);
  if(sock < 0) {
    perror("socket");
    exit(1);
  }

  struct sockaddr_in local;
  bzero(&local, sizeof(local));
  local.sin_family = AF_INET;
  local.sin_addr.s_addr = inet_addr(ip);
  local.sin_port = htons(atoi(port));

  if(bind(sock, (struct sockaddr*)&local, sizeof(local)) < 0) {
     perror("bind");
     exit(2);
  }

  if(listen(sock, 5) < 0) { 
    perror("listen");
    exit(3);
  }
  return sock;
}

int main(int argc, char* argv[])
{
  if(argc != 3) {
    printf("usage %s [IP][port]\n",argv[0]);
    return 1;
  }
  int listen_sock = StartUp(argv[1], argv[2]);

  char buf[64];
  struct sockaddr_in client;
  socklen_t len = sizeof(client);

  while(1) {
    pid_t pid = fork();
    if(pid == 0) {
      if(fork() == 0) {
        int sock = accept(listen_sock, (struct sockaddr*)&client, &len);
        if(sock < 0) {
          perror("accept");
          continue;
        }
        while(1) {
          ssize_t s = read(sock, &buf, sizeof(buf) - 1);
          if(s > 0) {
            buf[s] = 0;
            printf("client says# %s\n",buf);
            write(sock, &buf, sizeof(buf));
          }
        }
      } else {
        exit(0);//第一子进程退出由其父进程回收，而其子进程为孤儿进程，由一号进程回收。
      }
    } else {
      waitpid(pid, NULL, 0);//等待
    }
  }

  return 0;
}

//client.c

#include <stdio.h>
#include <strings.h>
#include <sys/socket.h>
#include <unistd.h>
#include <netinet/in.h>
#include <stdlib.h>
#include <arpa/inet.h>
#include <string.h>

int main(int argc, char* argv[])
{
  if(argc != 3) {
    printf("usage %s [IP][port]\n",argv[0]);
    return 1;
  }

  int sock = socket(AF_INET, SOCK_STREAM, 0);
  if(sock < 0) {
    printf("socket error!\n");
    return 2;
  }

  struct sockaddr_in server;
  bzero(&server, sizeof(server));
  socklen_t len = sizeof(server);
  server.sin_family = AF_INET;
  server.sin_port = htons(atoi(argv[2]));
  server.sin_addr.s_addr = inet_addr(argv[1]);

  if(connect(sock, (struct sockaddr*)&server, len) < 0) {
    printf("connect error!\n");
    return 3;
  }

  char buf[64];
  while(1) {
    buf[0] = 0;
    printf("please enter# ");
    fflush(stdout);
    ssize_t s = read(0, &buf, sizeof(buf));
    if(s > 0) {
      buf[s-1] = 0;
      write(sock, &buf, sizeof(buf));
      s = read(sock, &buf, sizeof(buf) - 1);
      if(s > 0) {
        buf[s] = 0;
        printf("server says# %s\n",buf);
      }
    }
  }
  close(sock);

  return 0;
}

基于TCP协议：多线程服务器

//server.c

#include <stdio.h>
#include <pthread.h>
#include <strings.h>
#include <sys/socket.h>
#include <unistd.h>
#include <netinet/in.h>
#include <stdlib.h>
#include <arpa/inet.h>
#include <string.h>

typedef struct Arg{
  int sock;
  struct sockaddr_in addr;
}Arg;

int StartUp(char* ip, char* port)
{
  if(ip == NULL || port == NULL) {
    exit(1);
  }
  int sock = socket(AF_INET, SOCK_STREAM, 0);
  if(sock < 0) {
    perror("socket");
    exit(1);
  }

  struct sockaddr_in local;
  socklen_t len = sizeof(local);
  bzero(&local, len);
  local.sin_addr.s_addr = inet_addr(ip);
  local.sin_port = htons(atoi(port));
  local.sin_family = AF_INET;

  if(bind(sock, (struct sockaddr*)&local, len) < 0) {
    perror("bind");
    exit(2);
  }
  if(listen(sock, 5) < 0) {
    perror("listen");
    exit(3);
  }
  return sock;
}

void Service(char* ip, int port, int sock)
{
  printf("[%s|%d] connected!\n",ip, port);
  char buf[64];
  while(1) {
    buf[0] = 0;
    ssize_t s = read(sock, &buf, sizeof(buf));
    if(s > 0) {
      buf[s] = 0;
      printf("[%s|%d]says# %s\n",ip, port, buf);
      write(sock, &buf, strlen(buf));
    } else if(s == 0) {
      printf("client %s quit!\n",ip);
      break;
    } else {
      perror("read");
      break;
    }
  }
}

void* server_client(void* ptr)
{
  Arg* arg = (Arg*)ptr;
  char* ip = inet_ntoa(arg->addr.sin_addr);
  int port = ntohs(arg->addr.sin_port);
  Service(ip, port, arg->sock);
  close(arg->sock);
  free(arg);

  return NULL;
}

int main(int argc, char* argv[])
{
  if(argc != 3) {
    printf("usage %s [IP][port]\n",argv[0]);
    return 1;
  }

  int listen_sock = StartUp(argv[1], argv[2]);

  struct sockaddr_in client;
  socklen_t len = sizeof(client);
  while(1) {
    int sock = accept(listen_sock, (struct sockaddr*)&client, &len);
    if(sock < 0) {
      perror("accept");
      continue;
    }
    Arg* arg = (Arg*)malloc(sizeof(Arg));
    arg->addr = client;
    arg->sock = sock;
    pthread_t tid;
    pthread_create(&tid, NULL, server_client, (void*)arg);
    pthread_detach(tid);
  }

  return 0;
}

//client.c

#include <stdio.h>
#include <pthread.h>
#include <strings.h>
#include <sys/socket.h>
#include <unistd.h>
#include <netinet/in.h>
#include <stdlib.h>
#include <arpa/inet.h>
#include <string.h>

int main(int argc, char* argv[])
{
  if(argc != 3) {
    printf("usage %s [IP][port]\n",argv[0]);
    return 1;
  }

  int sock = socket(AF_INET, SOCK_STREAM, 0);
  if(sock < 0) {
    printf("socket error!\n");
    return 2;
  }

  struct sockaddr_in server;
  bzero(&server, sizeof(server));
  socklen_t len = sizeof(server);
  server.sin_family = AF_INET;
  server.sin_port = htons(atoi(argv[2]));
  server.sin_addr.s_addr = inet_addr(argv[1]);

  if(connect(sock, (struct sockaddr*)&server, len) < 0) {
    printf("connect error!\n");
    return 3;
  }

  char buf[64];
  while(1) {
    buf[0] = 0;
    printf("please enter# ");
    fflush(stdout);
    ssize_t s = read(0, &buf, sizeof(buf));
    if(s > 0) {
      buf[s-1] = 0;
      write(sock, &buf, sizeof(buf));
      s = read(sock, &buf, sizeof(buf) - 1);
      if(s > 0) {
        buf[s] = 0;
        printf("server says# %s\n",buf);
      }
    }
  }
  close(sock);

  return 0;
}

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