linux Tcp 通信socket

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本文提供了一个简单的TCP客户端和服务端的C语言实现示例。客户端通过指定的主机名和端口号连接到服务端，并从服务端接收消息。服务端监听特定端口，接收客户端连接请求并发送问候消息。

#include <sys/types.h>   
#include <sys/socket.h>   
#include <arpa/inet.h>   
#include <netinet/in.h>   
#include <strings.h>   
#include <string.h>   
#include <stdio.h>   
#include <stdlib.h>   
#include <errno.h>   
#include <unistd.h>   
int main(int argc, char *argv[])   
{   
    int sockfd;   
    char buffer[1024];   
    struct sockaddr_in server_addr;   
    int portnumber, nbytes;   
    if (argc != 3) {   
        fprintf(stderr, "Usage:%s hostname portnumber\n\a", argv[0]);   
        exit(1);   
    }   
    if (inet_aton(argv[1], &server_addr.sin_addr) == 0) {   
        fprintf(stderr, "the hostip is not right!");   
        exit(1);   
    }   
    if ((portnumber = atoi(argv[2])) < 0) {   
        fprintf(stderr, "Usage:%s hostname portnumber\n\a", argv[0]);   
        exit(1);   
    }   
    // 创建套接字   
    if ((sockfd = socket(AF_INET, SOCK_STREAM, 0)) == -1) {   
        fprintf(stderr, "Socket Error:%s\n\a", strerror(errno));   
        exit(1);   
    }   
    // 填充服务器的地址信息   
    server_addr.sin_family = AF_INET;   
    server_addr.sin_port = htons(portnumber);   
    // 向服务器发起连接   
    if (connect(sockfd, (struct sockaddr *)&server_addr, sizeof(struct sockaddr)) == -1) {   
        fprintf(stderr, "Connect Error:%s\n\a", strerror(errno));   
        exit(1);   
    }   
    // 连接成功后，从服务器接收信息   
    if ((nbytes = read(sockfd, buffer, 1024)) == -1) {   
        fprintf(stderr, "Read Error:%s\n", strerror(errno));   
        exit(1);   
    }   
    buffer[nbytes] = '\0';   
    printf("I have received:%s\n", buffer);   
    close(sockfd);   
    exit(0);   
}

#include <sys/types.h>   
#include <sys/socket.h>   
#include <arpa/inet.h>   
#include <netinet/in.h>   
#include <strings.h>   
#include <string.h>   
#include <stdio.h>   
#include <stdlib.h>   
#include <errno.h>   
#include <unistd.h>   
int main(int argc, char *argv[])   
{   
    int sockfd, new_fd;   
    struct sockaddr_in server_addr;   
    struct sockaddr_in client_addr;   
    int sin_size, portnumber;   
    char hello[] = "Hello! Are you fine?\n";   
    if (argc != 2) {   
        fprintf(stderr, "Usage:%s portnumber\a\n", argv[0]);   
        exit(1);   
    }   
    if ((portnumber = atoi(argv[1])) < 0) {   
        fprintf(stderr, "Usage:%s portnumber\a\n", argv[0]);   
        exit(1);   
    }   
    // 创建套接字   
    if ((sockfd = socket(AF_INET, SOCK_STREAM, 0)) == -1) {   
        fprintf(stderr, "Socket error:%s\n\a", strerror(errno));   
        exit(1);   
    }   
    // 填充服务器的地址结构   
    bzero(&server_addr, sizeof(struct sockaddr_in));   
    server_addr.sin_family = AF_INET;   
    server_addr.sin_addr.s_addr = htonl(INADDR_ANY);   
    server_addr.sin_port = htons(portnumber);   
    // 套接字绑定地址   
    if (bind(sockfd, (struct sockaddr *)&server_addr, sizeof(struct sockaddr)) == -1) {   
        fprintf(stderr, "Bind error:%s\n\a", strerror(errno));   
        exit(1);   
    }   
    // 进入监听状态   
    if (listen(sockfd, 5) == -1) {   
        fprintf(stderr, "Listen error:%s\n\a", strerror(errno));   
        exit(1);   
    }   
    while (1) {   
        // 接收客户端的连接   
        sin_size = sizeof(struct sockaddr_in);   
        if ((new_fd = accept(sockfd, (struct sockaddr *)&client_addr, (socklen_t *)&sin_size)) == -1) {   
            fprintf(stderr, "Accept error:%s\n\a", strerror(errno));   
            exit(1);   
        }   
        fprintf(stderr, "Server get connection from %s\n", inet_ntoa(client_addr.sin_addr));   
        if (write(new_fd, hello, strlen(hello)) == -1) {   
            fprintf(stderr, "Write error:%s\n", strerror(errno));   
            exit(1);   
        }   
        close(new_fd);   
    }   
    close(sockfd);   
    //  exit(0);   
    return 0;   
}

原文：http://www.linuxidc.com/Linux/2011-05/35331.htm