TCP/IP套接字示例（Hello World改寫）

服務器端 tcp_server.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <sys/socket.h>
void error_handling(char *message);

int main(int argc, char*argv[]){
    int serv_sock;
    int clnt_sock;
    struct sockaddr_in serv_addr;
    struct sockaddr_in clnt_addr;
    socklen_t clnt_addr_size;

    char message[] = "Hello World!";

    if(argc != 2){
        printf("Usage : %s <port>\n", argv[0]);
        exit(1);
    }

    //調用socket函數創建套接字
    serv_sock = socket(PF_INET, SOCK_STREAM, 0);
    if(serv_sock == -1){
        error_handling("socket() error");
    }

    memset(&serv_addr, 0, sizeof(serv_addr));
    serv_addr.sin_family = AF_INET;
    serv_addr.sin_addr.s_addr = htonl(INADDR_ANY);
    serv_addr.sin_port = htons(atoi(argv[1]));

    //調用bind()函數分配IP和端口號
    if(bind(serv_sock, (struct sockaddr*) &serv_addr, sizeof(serv_addr)) == -1){
        error_handling("bind() error");
    }

    //調用listen()函數將套接字轉爲可接受連接狀態
    if(listen(serv_sock, 5) == -1){
        error_handling("listen() error");
    }

    //經過一下代碼則說明已經有了連接請求
    clnt_addr_size = sizeof(clnt_addr);
    clnt_sock = accept(serv_sock, (struct sockaddr*) &clnt_addr, &clnt_addr_size);
    if(clnt_sock == -1){
        error_handling("accept() error");
    }

    write(clnt_sock, message, sizeof(message));
    close(clnt_sock);
    close(serv_sock);
    return 0;
}

void error_handling(char *message){
    fputs(message, stderr);
    fputc('\n', stderr);
    exit(1);
}

客戶端代碼 tcp_client.c

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

void error_handling(char *message);

int main(int argc, char* argv[]){
    int sock;
    struct sockaddr_in serv_addr;
    char message[30];
    int str_len = 0;
    int idx = 0;
    int read_len = 0;

    if(argc != 3){
        printf("Usage : %s <IP> <port>\n", argv[0]);
        exit(1);
    }

    /**
    *創建套接字，但是此時套接字並不會馬上分爲服務器端或者客戶端。
    *需要依靠後面調用的函數，如果是bind或者listen函數，就會成爲服務器套接字；
    *如果是connect函數，將會成爲客戶端套接字。
    */
    sock = socket(PF_INET, SOCK_STREAM, 0);
    if(sock == -1){
        error_handling("socket() error");
    }

    memset(&serv_addr, 0, sizeof(serv_addr));
    serv_addr.sin_family = AF_INET;
    serv_addr.sin_addr.s_addr = inet_addr(argv[1]);
    serv_addr.sin_port = htons(atoi(argv[2]));

    if(connect(sock, (struct sockaddr*)&serv_addr, sizeof(serv_addr)) == -1){
        error_handling("connect() error");
    }

    while(read_len = read(sock, &message[idx++], 1)){
        if(read_len == -1){
            error_handling("read() error!");
        }
        str_len += read_len;
    }

    printf("Message from server: %s \n", message);
    printf("Function read call count : %d \n", str_len);
    close(sock);
    return 0;
}

void error_handling(char *message){
    fputs(message, stderr);
    fputc('\n', stderr);
    exit(1);
}

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成功！！！